We are moving!

Hey All,

Yeah Yeah I know, it’s been a while… But there is a legitimate reason I assure you! I’m in the middle of moving the blog across to my own server. The reason for this is quite simple. I’m really limited to what I can do to the pages here when hosted by Word press. So the blog will essentially be exactly the same (in a slightly different format) plus I have added a few little extra’s.

You can get to it two ways:

http://www.thebizzleblog.com

and

http://www.nodetonation.com

And introducing the new Bizzleblog / No Detonation Forums here at http://www.nodetonation.com/phpBB3/index.php

Everything is in development, nothing is really ready yet, but for those that use this as a technical resource this should make it a lot easier for us all to grow and share the archive of information.

See you over there!

Bizzle

CAM Auto Developments A++

Within our scene, we are very vocal about companies that deliver us poor service. It is however, unusual for anybody to pipe up when we do get exceptional service. Yesterday at about 3:30pm i ordered some Thermotec Black Exhaust wrap from CAM AUTO DEVELOPMENTS in Hertfordshire.

This morning at 9:25am the post boy landed it on my desk. That’s less than 18 hours from order to delivery, plus they included a nice bag of Haribo Star Mix (which is empty in the photo, as i promptly scoffed)

Credit where credit is due guy’s! Exceptional service!

http://www.camauto.com/

or their ebay shop

http://shop.ebay.co.uk/camautodevelopments/m.html?_nkw=&_armrs=1&_from=&_ipg=25

 

S.A.P RX7 Update (08/10/10)

Weeeellll Hellllo there!

It’s been a while since there has been an update on the FD but that doesn’t mean significant progress hasn’t been make.

So where are we at so far?

Last time you saw it (in an update exactly one month ago) it was in the bodyshop with various bits being prepped ready for paint. Well, she’s now back at home plate and all in 1 colour. I’m not going to do in-depth pictures here, i’ll take you around the car once it’s done. But needless to say, the quality of the paint finish is beyond exceptional. Really bloody impressive. It’s immaculate, i shit you not.

Painted in Bentley Beluga Black

I have also made a start on fitting some of the bits that i had “knocking around” !! I have undersealed all the arches (will do the entire underside of the car before im done) And fitted a set of brand new GReddy Type S suspension:

 

We also fitted another toy, a very pimp Shine Auto Projects carbon front under tray.

The other good news is that my young padawan Scott turned up with my rubber earlier on this week. We test fitted a couple of different spacer setups on a bare rim and have found something that works.  I’m just waiting for Mr Smeeeth at Garage D to get his order of “spethal” wheel nuts in on Monday/Tuesday and we may even see a “rim shot!” mid week.

What else is there to do?

I need to remove the complete exhaust and turbo setup from the car. Not only does it have no heat proofing, but it’s also got no baffles. It’s a single 3.5 inch pipe from the turbo back. On a street port it’s LOUD! There are also a couple of blown gaskets by the sounds of things.

The car also has a slight oil leak from the sump which is going to be an arse to fix, but i’ll jump on that at some point in the near future.

Fit the OMP block off plate (i’ll explain more about that nearer the time)

And i need to do something with the interior… i mean BADLY. It looks like a fecking war zone in there.

More as it happens.

How to build a drift car – S13 Project Pt 11

Holy shit…

I hate standard UK S13 spoilers. So as with many S13′s before i undid the bolts and manhandled it off the bootlid. I have done quite a lot of patch and fill jobs on S13 lids in the past but this one really took the bourbon. If you own an S13, the likelihood is that you’ll have a similar (albeit not so drastic) situation underneath your own standard spoiler. The problem is that the standard boot spoiler acts as some very convenient water trap, which over the 15-20 years of the cars live, gradually eats away at the metal – resulting in the above.

I must admit i have never seen one quite this bad.

Usually, i would have just binned the entire bootlid and purchased another one of the forums. However, this one had a tinted rear screen that matches the 1/4 windows AND i’m supposed to be helping show people how to build a solid street car. So, i guessed it would be helpful if i put the hours in to show you how to repair the problem on  your own driveway.

First and foremost, if you remove your spoiler and it reveals a similar scene to the one above, bin it. It’s really not worth your time. A new, rust free bootlid can be had off the for sale sections of  Driftworks or the SXOC for around £50 and it’s by far your easiest option. But if you really want to fix it, then do the below.

Firstly, you’ll need to remove the 4 bolts holding on the spoiler and the 3 bolts holding on the window motor. Then from the top of the bootlid, remove the cowl around the bottom of the wiper arm and undo the 12mm bolt and remove. The spoiler is held on with 4 poppers, 4 bolts and a load of shitty bondo/glue stuff. Forget trying to pop it all off in one piece after 15 years of rot and grime. Give it a good tug and the whole thing should pull off in a couple of bits.

That’ll leave you with this:

Firstly, you need to get rid of the rust… That means physically cutting it out of the lid – do to this, you’ll need either an angle grinder with a cutting disc or a small air saw or nibbler. Before you make any cuts, get a wire brush attachment on the end of a power drill or sand the surface back around the rusty area untill you find the point where the metal becomes “rust free” Make sure you check underneath and on top of the lid to confirm that you have got it all. Then mark up your cutting lines with a marker or scribe and chop away.

You’ll see on the right hand photo that i have gone around the edges of the right hand hole with a wire brush attachment to bring it back to bare metal. This is because im going to weld in a plate. Welding and plate in is BY FAR the best way to fix this problem if the holes are this big. The other option is to fibreglass over the hole. It’s a pretty simple process that involves “packing” the hole out to give you something to lay the glass onto (Cardboard is good for this) and then laying fibreglass repair putty and sheets of glass fibre over the top. It’s not pretty and it’s not foolproof – but it works on smaller patches (really not anything this big tho)

As we are welding in a plate, the next stage is to make a template (out of card) for the plate that we need to fill the hole with. Make your template, check it fits, lay it on top of your plate and replicate. Simples.

Bend your plate to fit and tack it into the boot lid. You need to make sure that your plate is tacked ever so slightly recessed into the hole as you need to get a skim of filler in the top to bring it back up level.

Take a grinding disc on your angle grinder and grind off any very high points on your welds and bring them down level with the lid surface then very gently with a hammer, tap the edges of the now patched hole so ever so slightly bend them inwards (only very slightly tho) Then throw in a skim of filler.

At which point, i totally ran out of both light and  dry weather. So i’ll update this post with a second part in a day or so.

How to build a drift car – S13 Project Pt 10

Hey Folks,

I have had one or two mildly abusive emails from people complaining that I don’t update this blog enough. The jist of it is that i need to get off my newly married, KFC chomping backside and actually do some work on the cars.  So with that fresh in my mind, i gave the workshop a bloody good tidy up and cracked on with this part of the project.

What the f**k is holding you up, you ask? Well – nothing really, it’s mainly time. But now the wedding is out-of-the-way things should progress a bit quicker.

In the time-honoured tradition of the BBC’s Fast Show: “This week i have been mainly working on intercoolers”

The Intercooler:

Intercoolers are important bits of kit on drift cars especially as they function as a bloody great big heat exchanger for your inlet charge. (the air that goes into your engine) On a normally aspirated (N/A) car, the air is sucked in through an air filter and straight into your engine. So providing you keep your underbonnet temperatures low and feed it with nice cool air from a vent etc, you’ll be fine.

A turbo car however, is a very different kettle of fish. The turbo acts as a bit fat air pump pushing air into the engine but because it’s powered by the exhaust gasses the turbo get’s mighty hot. This in turn also heats up the air that’s pushed through the turbo, into the engine.

An intercooler (or specifically an air to air intercooler) acts to cool that air. As the charge passes through the inside of the intercooler, it’s heat is exchanged with the air flowing across the outside of the intercooler – thus reducing it’s temperature and cooling the charge.

Why is cooling the charge so important? Well, basically pre-ignition (what we call det) is caused by the gasses in the cylinder igniting before the piston reaches top dead centre on it’s combustion cycle. This results in the explosion trying to push the piston back down the bore, while the crankshaft and connecting rod are trying to push it up. This is BAD NEWS.

Pre Ignition/Pre Detonation can be caused by a number of things, but one of the main culprit is what we call “auto ignition” To explain auto ignition, you have to understand a principle called adiabatic heating effect. Adiabiatic heating is the effect by which any fluid/gas increases in temperature under pressure/compression. If you think that when a piston is on it’s up cycle, it’s job is to compress the air and fuel into a small space in the combustion chamber where the spark plug then ignites it and that dense packed pocket of gas explodes and expands with great speed and ferocity, pushing your piston down the bore.

When the piston compresses the gas, it dramatically increases in temperature. If the temperature of the air coming in to the engine is too warm, the adiabatic heating effect pushes the temperature of the combustion mix past the auto ignition point of the gasoline (about 280 deg c depending on the octane), causing it to self ignite before the spark plug fires.  Ala Det.

On a road car like the S13, you’ll see a natural “seat of the pants” power gain by fitting a Front Mounted Intercooler (FMIC) without doing any other supporting mods. This is because the effect of cooling the air actually makes it more dense. Simply, denser air makes a bigger bang = more power.

Mounting the cooler

There are a couple of possibilities for mounting your intercooler.

Standard Position

I tend to favour the simpler “standard” position you see above. It’s quick, easy and does exactly what you say on the tin (cool the charge) it gives the intercooler loads of cool air flow. It has three disadvantages. 1) It’s hanging off the front of the car, so it’s easier to hit it when drifting. 2) The air that travels through the intercooler into the radiator is warmer than if it was mounted in say, a Vee setup. 3) You use longer intercooler piping which can have an effect on throttle response. However, it’s pretty negligible if im honest.

V-Mount

V-mount setups move the intercooler up into the engine bay and direct the air using ducting. It places the intercooler and the radiator in a V position that allows them to both be fed by cool air at the same time removing the need for one to flow warm air into the other. You also have very short intercooler piping which delivers a nice, crisp throttle response. In addition you are also moving the cooler off the front of the car, which means that it’s less susceptible to damage.  There are some significant downsides to this setup however. It’s complexity requires lots of custom ducting and mounts to be fabricated as there are no “off the shelf” kits available for the S13. The other issue is due to the intercooler’s proximity to the engine it’s self, something called “Heat Soak” often occurs which (in layman’s terms) means that the temperature of the intercooler it’s self, becomes more or equal to the air traveling through it. The engine effectively heats up the intercooler and there isn’t enough cool air to reduce its temperature.

While a v-mount setup may look cool, unless your building a straight competition car – Keep It Simple.

How I did mine

There are two main points for mounting your intercooler.

1) Make sure that the bottom of the intercooler is higher than the bottom panel of the chassis. Otherwise, you’ll be smashing it on everything in sight.

2) Make sure that there isn’t anything obstructing the air flow to the intercooler. You’ll see from my picture above that i have cut about 2/3rds of the standard bumper support bar and replaced it with a piece of round bar. While this won’t offer much protection during an impact. It does keep the bar in one piece, support the bumper and adds a little bit of extra strength to the remaining corner pieces.

3) Make it strong. There is nothing worse than somebody who half heartedly bolts on an intercooler that flaps around all the time. You shouldn’t be able to wiggle or move it once it’s on. If there is any movement, it will only result in your boost pipes wiggling loose and falling off without prior notice. If your really unlucky, it’ll cause one of the bloody annoying boost leaks that you can’t find easily and spend the next 8 hours faffing with.

I made up a nice support bar for mine, which i painted up and fitted on the top. There are also two fabbed brackets below to keep it all secure.

Painted

On the car

At the end of the day an intercooler is an intercooler. Don’t go spending thousands on GReddy or HKS branded ones. It’ll just get bent and trashed. XS Power is a crappy ebay brand fo’sho. But it’s made in exactly the same factory as the Autobahn or other UK branded ones (no names mentioned) They all cool air in the same way

Other than intercooler fitting, i fitted a front tow hook (which is almost a necessity when skidding on track)

I also finally got the exhaust back on. I need to make up a couple of extra brackets to make sure it’s all secure, but she’s on. Quick bizzle tip when mating up exhaust surfaces. Don’t use that crappy exhaust paste – it’s brittle and ‘orrible. Get some good quality clear silicone sealer (similar to the stuff you put round your bath tub) it’s what Nasa used to stick on the ceramic tiles to the space shuttle. It’s far better. Put a light smear on either side of your connecting gasket and do it up tight.

More as it happens.

S.A.P RX7 Update (08/09/10)

Hi chaps,

More piccy’s for you – these photo’s were taken yesterday. However i got a text from mat at 08:51am this morning telling me that the shell was now primed and all that’s left to prime up are the doors and boot lid. That means that they have been on it from some ungodly hour this AM.  Epic Effort.

If you’re not familiar with the painting process, this is a quick explanation of where we are at the moment. The car has had a “test fit up” which means all the panels and kit have been bolted up properly to check all the gaps are correct. The various modifications have been made where applicable and any obvious damage has been fixed with bondo/filler. The whole shell and its various panels are sanded flat and then the car is then disassembled again. Everything is then given a couple of coats of primer which acts as a) a good base for the paint and b) allows some of the very minor remaining imperfections in the bodywork to be sanded out so the surface is completely 100% smooth.  In the pictures below you’ll see that there is (what looks like) black spray paint dusted over all the primed panels. This is called “Guide Coat” and it’s purpose is to highlight any area’s of imperfection on the panel. The idea is that when you hand sand the primed panel, you’ll take the guide coat off the flat areas and it’ll remain in any areas of slight indentation of imperfection. You then either lightly sand the primer untill that imperfection is gone and the surface is level or for anything substantial, you can apply a very light skim of filler and then re-prime and repeat. Clever huh?

(remember, click for biggies!)

Skirts

Wings

Front Bumper

Rear Bumper

Booth full of bits

Naked FD…

The bonnet before primer…

S.A.P RX7 Update –

Ahoy chums,

I’m trying to find some witty comment to make about my recent nuptials, but frankly married bizzle is no different un-married bizzle, apart from the fact my left ring finger is clamped with silver and the wife now owns half of everything.  Harsh but true.

Real life bulshit out of the way, i received an email with some pictures of the RX7′s progress up at Carbody Banbury. Matt (Dori-matt) of Driftworks has been doing a stirling job of keeping me up to date with it’s progress.

Remember, Click for Biggies

Please excuse the super wankey wheels, weak offset, wank stance and poor ride height. I promise i will make a mense.

Rear over-fender arches fitted and smoothed through

Need…wider…wheels….

The idea on this car was to compliment the line of the car with any changes that we made. The motto “less is more” came to mind (yes yes, i know that im fitting stupid fucking wheels to it) So with that said we have removed the rear wiper and spray nozzle then welded and filled all the holes. This should give it a nice smooth, subtle look.

Boot

We also removed the standard wing mirror holes (they are mounted in the door as standard) as this car has had the mirrors incorporated further up.

Just a quick pic to show how well it the kit fits. I’m told there was little or no fettling what so ever

More as it happens.

How to build a drift car – S13 Project Pt 9

Hey again folks,

Well, the S13 has been sat in her bay getting tinkered with every couple of weeks. I have been concentrating on some real life stuff of late and have also just picked up the new FD project (see here) which has taken up a little of my ever decreasing free time. We are actually not too far away from getting the S13 road worthy again. The main bits that need to be done are:

- Purchase and fit rear 1/4 panels

- Get hubs back from clarkey and install

- Sort out wheels

- Bleed brakes/clutch system

- Fit exhaust and another bit of tidying up here and there.

Arch Modifications

About a month or so ago, i cut, rolled, welded and sealed  the rear 1/4 panels to enable them to accept some more manly wheels and offset. The reason for this isn’t actually for aesthetics, it’s to enable me to run a wider footprint and get the car lower to the ground. A larger footprint (distance between the wheels) actually adds stability to the  platform by lowering the centre of gravity. A common analogy used is that of a match box. What’s easier to push over, a matchbox on it’s end or a matchbox on it’s side?

The above is a personal choice of setup, to match the slightly wider footprint of the S14 rear subframe.

Pulling the arches involved cutting the lip of the arch off and splitting the outer and inner arches from each other. The inner arch is then cut into “tabs” and the outer arch is rolled out and pushed outwards and upwards to create the larger arch profile. Once complete, the tabs are clamped to the outer arch and tacked/welded back together.

The next (and probably most important step) is to seal the underside of the arch with something like “Grey Stripe Seem Sealer” (available from all good automotive hardware shops) and then under seal the arch to create a rustproof moisture resistant seal. The outer arch is now ready to have an aftermarket 1/4 panned fitted over the top.

Steering Arms

With the departure of the R34, i had a nice set of Tein tie rods and ends knocking about. I decided it would be a bit criminal not to put them onto the S13 project as ultimately i needed some anyway! For those that don’t know, the whole premise for using the aftermarket tie rods are two fold.

1) They are considerably thicker/stronger than the standard items

2) They allow the rod to travel FURTHER into the rack, providing extra steering lock over standard

The threaded connector that screws into the rack is longer on Tein rod than on a standard one. This means that with the aid of a small spacer (seen in the middle top of the above tool picture) more of the rod can travel into the steering rack giving more steering angle. Geddit?…. no?…. okay, i’ll do a diagram. Screw you chaps for making me embarrass myself with my epic MS Paint Skilz.

Top one is standard, bottom one is Tein.

Okay, so this is the right hand side of the rack. The grey is the tie rods, the black blocks are the inner rack (with the rods screwn into them) and the empty square box is the outer rack. See that yellow block? That’s the spacer that goes between the inner rack and the rod. This allows the tie rod, to travel further into the rack, ya see…

Top one is standard, bottom one is Tein, this time, on lock.

So now you see, the bottom tein rod can travel further into the rack, thus pulling the wheel further (and pushing the opposing one) giving you more lock. Cool huh?

Below is the standard setup on the car before i changed them -

Basically you undo the twisty tie and pull the boot back to reveal the ball joint.

The red arrows show the tabs on the washer that need to be pried back so that the rod can be undone. I then use a large pipe wrench to undo the old arm and gently re-install the new one. The moog joint on the hub end of the tie rod needs to be removed with a 17mm socket and then removed with a ball joint splitter or (my prefered method) firmly thwack the hub (DON’T HIT THE JOINT) with a hammer.

I’ll insert a competed picture here later on this evening.

More as it happens….

Introducing the Bizzle S.A.P RX7 FD3s

Ahoy their chums,

It’s been a little while since i gave the bizzleblog anything fresh – the bottom line for this is simple. In two weeks (pretty much to the day) i’ll be tieing the knot with my long suffering “other half” overseas and she’s commandeered every penny that i own to pay for an expensive overseas wedding.

Bizzle Tip for the day: “Don’t fucking get married – it’s more expensive than you can imagine”

I was having this conversation with young Mr Flappy Hands (Phil “FlikstRR” Maclachlan – check out his new PS13b project) the other day over MSN, when i realised that my new engine for the R34 actually magically transformed it’s self into a lavish wedding breakfast. Anyway… enough about that.

With the Bizzleblog S13 requiring some final finishing touches (more about that in later articles) and me getting sick of the sight of the R34 4 door stuck on axle stands with a wedding breakfast for an engine and a champagne toast for a turbo – so i put it up for sale (or preferably swap) with something that i could jump in and drive pretty quickly.

The next morning i got a PM on Driftworks by a nice chap who owned an RX7 FD3s that was in his words “95% finished” and he was interested in swapping it with me for the rolling R34 shell. After a lot of back and forth, we did a deal that worked for both of us. The only problem was, i had to get the R34 on 4 wheels and rolling before i could put it on a trailer!

Need wheels....

The second problem was that i had used the R34 as a bit of a Christmas Tree for the past couple of months and pinched loads of bits off her for various other endeavors. So a trip up to see my old friend Mr Smith at Garage D was in order. I hadn’t been up there in a while and the rumor was that you need to make an “appointment” these days. So a quick phone call to Eoin, who looks after all parts sales for Garage D and i arranged a time to pop up and see them.

If you have never had a reason to go visit their workshop in Watford, go buy something just for the experience. You’ll struggle to find a larger concentration of “tite as fuck” skyline’s and parts anywhere else in the UK. I have known Julian since he used to work out of a small workshop on the other side of Imperial Way – to this date, i have never been to him and asked for a part he didn’t have sitting on the shelf (and im talking about some proper obscure stuff too)

With the parts kindly passed over to me by Eoin and some dosh exchanged, i was on my way back to home plate with all the bits i needed to get the car rolling and onto the trailer.

All that was left was a quick Sunday afternoon dash down to Bristol to exchange the cars and bring the FD back to the fort.

And here she is…

So far the spec of the car is:

1993 RX-7 FD3s 2+2

Street ported engine built by RX Motors containing:

- Street port
- New standard apex seals etc
- Polished Plenum & Throttle Body
- GReddy Pulley Kit.

GReddy turbo kit containing:

- GReddy Air Filter
- GReddy Turbo Elbow.
- GReddy Downpipe.
- GReddy Exhaust Manifold.
- GReddy External Waste gate.
- GReddy Screamer Pipe.
- GReddy TD06 SH25G Turbo.
- GReddy Turbo Heat shield.

Additional Engine Ancillaries:
- 1600c Injectors (secondary)
- Primary injectors 550cc
- GReddy FMIC
- Secondary Fuel Rail Kit
- Apexi Power FC ECU and commander
- Aeromotive Fuel Pressure Regulator

- HKS Exhaust & Decat
- Bosch Fuel Pump 044

I also got A LOAD of very cool bolt on bits to go with her. The front bumper (and the rest of the kit) is genuine Shine Auto Project (Burnout kit)
There are a number of things that need doing to the car, she’s currently got no boost controller or fuel map and the exhaust system seems to have had proper gaskets substituted for exhaust paste (retards) The engine has only just been fitted after being “run in” in a different vehicle which make an unfortunate contact with a concrete lamp-post. The sump also has a slight leak and the paint work is in need of some serious work to tie the whole car together.

Luckily, she’s currently sat up with the chaps at CarBody Banbury who are going to work there magic with her.

I’ll keep you updated with her progress over the coming months, but having a running and driving car is a definite step in the right direction!

I’ll leave you with a link of her running on a base map

CLICKY CLICKY

High Compression Ratio FI Engines

This is an article I have been compiling over the last couple of months on running higher compression ratios in some of the RB/SR/JZ engine’s. It’s a very hotly debated subject at the moment and the two camps are extremely divided. As a lot of you probably know, the two “camps” consist of the old school Cosworth era tuners who have been building engines with lowered ratio’s for years (and have worked well) and the newer breed of tuners (mainly stemming from USDM Honda scene) who have had great practical and proven success building higher compression turbo engines.

Let’s start with the correct turbo choice for your application.
People run smaller turbo’s because they want them to spool early and to deliver a wider range of power. Turbo A (smaller turbo) running 1.0bar will spool faster than Turbo B (slightly larger) running the same boost pressure, but the amount of air moved by Turbo B (slightly larger) will be greater at the given boost pressure as it’s moving more air? Thus creating more power. Follow me?

The problem is that the more boost pressure you run, the more the charge is heated by the turbo. This results in the temperature of the air/fuel mix entering the combustion chamber to be significantly higher. Once the piston is on it’s up stroke, this air and fuel mix is compressed and something called adiabatic heating occurs. (*which is the increase in temperature of a fluid when under pressure) if this air fuel mix reaches the auto-ignition point of gasoline you get premature detonation or det (The air/fuel mix auto igniting before the spark plug fires – not like premature ejaculation)

By upping the compression ratio in an engine, your increasing the heat that is generated when the gas is compressed on the upstroke (but also increasing the density of the gas/air mix and extracting more mechanical energy) this means that your inlet temperatures and fuel octane are significantly more important. Higher octane fuel has a higher auto ignition temperature and is more difficult to burn (the opposite to common belief that high octane fuel is actually more easily ignited) thus making your combustion process more det resistant.

The type of piston and shape of the combustion chamber, determines the speed of the flame front that travels across the compressed mixture.

In simple terms a higher compression ratio DOES create more power off boost which gives you extra torque down the arse end. It’s really down to static vs. effective compression.

(excuse the cut and paste math below)

Effective compression is the sum of the static compression, plus the additional compression added to the cylinder by a turbo or super charger, or any other forced induction tool for that matter. Effective compression is defined by the following formula:
E = C((B / 14.7) + 1)
Where E= Effective Compression, B= boost psi, and C= Static compression. Also remember that 14.7 is equal to 1 bar of boost.

Let’s do an example. Let’s say we have a SR20DE bone stock with 10.4:1 static compression and slapped on a turbo kit. It’s now boosting 7psi. That takes care of our variables. Let’s do the math.
E = C((B / 14.7) + 1)
E = 10.4((7 / 14.7) + 1)
E = 10.4((.476xx) + 1)
E = 10.4(1.476xx)
E = 15.35xxx
As you can see, we come up with an effective compression ratio of 15.3 or so. A motor in this effective compression range is easily daily driven with proper fuel and timing adjustments/upgrades.

(Running on the same turbo back to back)

If you’re running a 9.0:1 compression ratio @ 1 bar you’ll achieve an effective compression ratio of 18:1

If you’re running a 7.5:1 static compression ratio and 1 bar of boost you achieve an effective compression ratio of 15:1.

For the 7.5:1 to reach the same effective compression ratio you need to run .4bar or 5psi more boost. Combined with the fact that you have less “grunt” outside the boost threshold. Less grunt/torque means your engine produces LESS of a bang when the combustion mixture ignites, along with a slower burn due to a less compressed cooler mixture.

So in a nutshell – if you’re running 2.0 bar of boost on a 7.5:1 static ratio your achieving an effective compression ratio of 22.5:1 if you run the same setup with 9.0:1 static ratio you get the same effective compression ratio but with only 1.5 bar of boost and much better drivability outside of the boost threshold and a better spool due as a result.

Of Course, if the compression ratio is too high then the adiabatic effect will cause the mixture to auto ignite – so there is a line to be drawn obviously.

When building turbo engines static compression ratio is actually a bit of a clumsy way of measuring what’s going on because your measuring the C/R at atmospheric pressure not the desired. With that said, a higher C/R engine will produce more power off boost and subsequently spool your turbo slightly faster. You need to aim for a power goal (whatever that is) and spec your turbo setup accordingly to produce the required air at a reasonable pressure & temperature.

The majority of the above article should be considered when building any engine

Notes:
* Air is a fluid