Compression Ratio - What should you choose with new pistons?

[Imperial_16v]

Afternoon all. :)

I'm looking still at what parts you can get for the F7R and wondered when buying pistons, what compression do people get?

Firstly, has anyone heard of Pure Performance Motorsport and their pistons? Link below:

http://www.pureperformancemotorsport.com/shop/product_info.php?cPath=105_211&products_id=401&osCsid=4a756b0f2c4811b0dc9f83195e1de40a

All I know is that the bore is 82.7mm on the F7R. But should you go for as close to 10:1 (standard) as possible, so in this case 11:1. Or just go the whole hog and get the highest compression (12.5:1) and run higher octane fuel?

Does the Williams have a knock sensor?

I was then going to get the H-rods from the same company also:

http://www.pureperformancemotorsport.com/shop/product_info.php?cPath=105_210&products_id=157&osCsid=4a756b0f2c4811b0dc9f83195e1de40a

Thanks! 8)

[Wobba]

Not used them myself, other will know of them.

As for the compression, it depends what you want. Deviating from OE is fine but you need to make sure you are building the engine to a finely tuned spec when you are doing this sort of thing to ensure longevity and performance.

You can go higher than 12.5:1

You will need to have it custom mapped if you go over the OE spec or else detonate the car to death pretty fast.

What do you use it for?

I've got 12.5:1 at the mo.

[Imperial_16v]

Not used them myself, other will know of them.

As for the compression, it depends what you want. Deviating from OE is fine but you need to make sure you are building the engine to a finely tuned spec when you are doing this sort of thing to ensure longevity and performance.

You can go higher than 12.5:1

You will need to have it custom mapped if you go over the OE spec or else detonate the car to death pretty fast.

What do you use it for?

I've got 12.5:1 at the mo.

Thanks for the reply Wobba.

I don't have a Williams yet, still saving. But with regards to what I will use it for, it will just be a weekend car. :)

I was planning to strip and build the engine back up to standard, with genuine OE parts. I plan to stick on just an IK and put in some catcams 225's and then get a remap done for the time being. Then when I can afford it, upgrade to some ITB's.

Would you suggest just going for 11:1 ratio instead? I read that the higher the compression the higher the power output.

Is it easy enough to say to a tuner it's running 12.5:1 compression, please adjust the map to fit?

Thanks.

[Wobba]

Higher compression leads to a better volumetric efficiency (a better bang).

I think it's about 3% bhp increase over what the engine normally makes, per full point of compression. So for 12.5, its 7.5% over normal compression.

It's a good idea to tell a tuner before they go mapping the car what mods are on it, though tbh they will just treat it as a bespoke engine anyway and listen out for detonation and give that that engine can accept without damage occurring, they wont just put a base map on and walk away. If they do, they suck.

The con rods are a good idea if you are revving consistently high rpm, as stock ones will die with high rpm. I tend to be in the high rpm zone quite a lot now as that's where most of my power is to be found, so they are forged Wossner items with ARP bolts too for good measure.

The ratio you go for is up to you. A well built high comp at 12.5 is fine as long as it's done right.

[chip]

Higher compression leads to a better volumetric efficiency (a better bang).

Volumetric efficiency is a term meaning how well the engine swallows air, ie what percentage of its static cylinder volume it manages to swallow each cycle, its not effected by CR to any significant extent.




I think it's about 3% bhp increase over what the engine normally makes, per full point of compression. So for 12.5, its 7.5% over normal compression.
Bit of a generalisation but you're kind of along the right lines, but the thing to mention as well is that too much CR in the midrange (where the engine naturally has higher VE in the first place) can result in you having to withold timing to prevent detonation, and this in turn will LOSE you power at that point.

At higher RPM though, its more or less a case of the higher the CR the better.




It's a good idea to tell a tuner before they go mapping the car what mods are on it, though tbh they will just treat it as a bespoke engine anyway and listen out for detonation and give that that engine can accept without damage occurring, they wont just put a base map on and walk away. If they do, they suck.

The con rods are a good idea if you are revving consistently high rpm, as stock ones will die with high rpm. I tend to be in the high rpm zone quite a lot now as that's where most of my power is to be found, so they are forged Wossner items with ARP bolts too for good measure.

The ratio you go for is up to you. A well built high comp at 12.5 is fine as long as it's done right.
Agreed on all that.

[Imperial_16v]

Brilliant, cheers for the help. :D

One final question, after it is all built will I be OK driving to the tuning company? Or is it best to get the car towed their or trailered? Just with what has been said about detonation due to the increase compression ratio, I'd hate to break the thing before it's even begun! :wink:

I'm thinking that I may just stick with 11:1, as with the info chip has provided I would use mostly low-mid range power for day to day driving, which is different to Wobba and using high rpm.

Thanks!

[chip]

I wouldnt drive a high comp motor AT ALL on a low comp map, not even gently personally, its not worth the risk.

[Imperial_16v]

I wouldnt drive a high comp motor AT ALL on a low comp map, not even gently personally, its not worth the risk.

OK thanks Chip.

I'd have to get a tow to the tuning company then. Would that be OK?

Am I OK to start the motor and leave it to idle. What I am thinking is I'd like to fire it up after the rebuild, see what happens! :D

[chip]

What management are you planning on running?

If its the standard setup still (requires single throttle inlet not ITBs) Im sure KJ16V could send you a basemap for 11:1 that would be ok to then drive to him for a proper map.
If its aftermarket then just get someone who knows how to map to be there when you start it up.

[Imperial_16v]

What management are you planning on running?

If its the standard setup still (requires single throttle inlet not ITBs) Im sure KJ16V could send you a basemap for 11:1 that would be ok to then drive to him for a proper map.
If its aftermarket then just get someone who knows how to map to be there when you start it up.

Yeah would be Standard management for now. Thanks for the info, I'll make sure to get in touch when the time comes. Still need to buy my williams first. lol.

Cheers for all the help peeps!

[chip]

Well if you are sticking with the standard management then get friendly with kj16v, as not many other people can be bothered to piss around with the antique management on these cars, so even though from what I gather he hasnt been mapping very long yet he is alredy a really useful resource for people who stick with it just cause he is bothering with it when most tuners would throw it away and fit something decent instead, and ive only heard good reports of his work so far.

[Imperial_16v]

Well if you are sticking with the standard management then get friendly with kj16v, as not many other people can be bothered to piss around with the antique management on these cars, so even though from what I gather he hasnt been mapping very long yet he is alredy a really useful resource for people who stick with it just cause he is bothering with it when most tuners would throw it away and fit something decent instead, and ive only heard good reports of his work so far.

OK thanks again. I was also recommended to a chap called Paul at RSTuning in Leeds by Craig from AP-Developments.

[chip]

RS Tuning is an established company with plenty of overheads and hence have to charge accordingly, the cost of getting your car mapped by them would be encouraging me towards aftermarket if I were you TBH.

NOTHING wrong with what they do IME, Paul is a good tuner, but having a 400 pound map on a 20 quid ECU seems a bit pointless to me.
(not exact price, but along those lines)

[Imperial_16v]

RS Tuning is an established company with plenty of overheads and hence have to charge accordingly, the cost of getting your car mapped by them would be encouraging me towards aftermarket if I were you TBH.

NOTHING wrong with what they do IME, Paul is a good tuner, but having a 400 pound map on a 20 quid ECU seems a bit pointless to me.
(not exact price, but along those lines)

What advantages would I see from going with an aftermarket solution? What product would you recommend?

Cheers. :D

[chip]

Main advantages:

TPS verus RPM for main load tables means that you can run agressive cams without the ECU misunderstanding what is going on (the pulses coming back through the standard inlet make it impossible to map properly around)

Not tied down to just a handful of people who can be bothered to map it, if you go aftermarket you have your choice of tuners

Can easily change to multi throttle inlet

Additional features that might be useful like launch control or traction control potentially (less of an issue on a low powered N/A build)



In terms of actual power output at full throttle, no real advantage though, the mapping requirements of an N/A engine on full song are pretty simple.



What would I recomend?
Whatever someone near you that you trust to map your car recomends really, any modern aftermarket setup will do it realistically.

In terms of being easy fitment, sideways danny does the canems ecu which understands 44-2-2, as does megasquirt and mtec v4.
If you swap to a 172/megane flywheel though you then arent restricted to ones that understand the renix 44-2-2 setup, plus you can go wasted spark then too.

[Imperial_16v]

Main advantages:

TPS verus RPM for main load tables means that you can run agressive cams without the ECU misunderstanding what is going on (the pulses coming back through the standard inlet make it impossible to map properly around)

Not tied down to just a handful of people who can be bothered to map it, if you go aftermarket you have your choice of tuners

Can easily change to multi throttle inlet

Additional features that might be useful like launch control or traction control potentially (less of an issue on a low powered N/A build)



In terms of actual power output at full throttle, no real advantage though, the mapping requirements of an N/A engine on full song are pretty simple.



What would I recomend?
Whatever someone near you that you trust to map your car recomends really, any modern aftermarket setup will do it realistically.

In terms of being easy fitment, sideways danny does the canems ecu which understands 44-2-2, as does megasquirt and mtec v4.
If you swap to a 172/megane flywheel though you then arent restricted to ones that understand the renix 44-2-2 setup, plus you can go wasted spark then too.

You've said a whole load of stuff there that I don't understand! :lol: However, I will take a look at Canems ECU, Megasquirt and Mtec v4 and I'll also speak with RSTuning and see what they say. :D

Cheers!

[chip]

Sorry mate, which bits dont you understand, I will elaborate.


To cover the main points though.


MAP or TPS
MAP = Manifold absolute pressure
TPS = Throttle position sensor

Basically the ECU can see how hard the engine is working one of two ways (well 3 really as some cars have airflow meters but ours dont) one is to look at the pressure drop in the inlet, the other is to look at how far the throttle is open.
For performance N/A applications (particuarly ITB ones) you are better off with the TPS, its more accurate, especially at part throttle on big cams where you can get weird wave effects going on in the inlet manifold from the fact that the engine is breathing back out into the inlet manifold towards the middle of the compression stroke.





Renix 44-2-2
The standard flywheel crank sensor has a 44 teeth pattern with 2 misisng at the top and 2 missing at the bottom, this allows the ecu to see the engine is turning, and what speed its turning at and how far through the stroke it is etc, but it doesnt allow it to see which cylinders are the ones about to reach the top, ie it knows that 2 cylinders are at the top but not if they are 1 and 4 or 2 and 3, which means you cant run a wasted spark (coilpack) ignition setup on it.

[dhay14]

@chip nice explenation there mate

[Imperial_16v]

Hi all

Just to say, RS Tuning have been back in touch and do not recommend Megasquirt. They have advised this:-

http://www.tour-de-force.co.uk/ec/

They can do this with a loom, and all the mapping. Happy days! :D

[Laine_16v]

Hi all

Just to say, RS Tuning have been back in touch and do not recommend Megasquirt. They have advised this:-

http://www.tour-de-force.co.uk/ec/

They can do this with a loom, and all the mapping. Happy days! :D

Lol no surprises there!

[Imperial_16v]

Hi all

Just to say, RS Tuning have been back in touch and do not recommend Megasquirt. They have advised this:-

http://www.tour-de-force.co.uk/ec/

They can do this with a loom, and all the mapping. Happy days! :D

Lol no surprises there!

Uh-oh, that doesn't sound too good... is this not a good ECU to go for??? :oops:

[Wobba]

No, it's just different tuners have different preferred products to use. This is often because they will have a good deal for that product. The prices listed tehre for the loom and ECU look expensive though. What are RST pricing it at?

The F7R Clio is a basic piece of kit. You don't need an all singing, all dancing aftermarket ECU to make it work. As long as the product has good support and is easy to use, it will be fine. My Emerald K3 has waaaaaay more functions on it than I will ever use.

Do some research on it first though on the web.

[zmaster2k]

Friend of mine runs a TDF setup on his f4r with bodies, fantastically setup! I was extremely impressed car feels electrifying! But then I can't really comment on the ECU?! Just it's a very tidy setup indeed.

[Imperial_16v]

No, it's just different tuners have different preferred products to use. This is often because they will have a good deal for that product. The prices listed tehre for the loom and ECU look expensive though. What are RST pricing it at?

The F7R Clio is a basic piece of kit. You don't need an all singing, all dancing aftermarket ECU to make it work. As long as the product has good support and is easy to use, it will be fine. My Emerald K3 has waaaaaay more functions on it than I will ever use.

Do some research on it first though on the web.

Thanks mate, I think they said £599 (can't remember if that was plus VAT or not). Is that a resonable price? They didn't say which version of the ECU it was, looks like there are 3 to choose from though.

Cheers. :D

[Imperial_16v]

Friend of mine runs a TDF setup on his f4r with bodies, fantastically setup! I was extremely impressed car feels electrifying! But then I can't really comment on the ECU?! Just it's a very tidy setup indeed.

Good to know though! Thanks for the info. :)

[zmaster2k]

However I can comment on kj16v's mapping as he transformed my car!

[chip]

I dont think you will find any traditional tuning company who will recomend megasquirt and its for good reason IMHO
The product itself has some minor issues like the connector plug isnt really ideal, but more important than that is the total lack of tracability of some of the units, it could have been built by someone who doesnt know what they are doing and one dry injector output soldered joint is all you need to melt an engine.

If built properly they work well, but no tuner generally wants to get involved in something to shit and miss in terms of build quality.

If you go for the Mtec though, you get all the advantages of the megasquirt (some of the best mapping software in the world, amazing list of features and supported architecture such as the 44-2-2 etc) but with none of the risks ascociated with build quality as all their V4 units are machine assembled in a proper ISO approved factory etc.
Ive been running a V4 on my clio for a couple of years now without any problems at all, first on standard engine, then on bodies, then on a custom inlet, now im going for a 60-2 flywheel setup instead and I know it will cope with that fine too with a few simple tweaks, its a very easy ECU to work with.

[Imperial_16v]

However I can comment on kj16v's mapping as he transformed my car!

I might actually get in touch, as costing in the ECU (including the VAT) plus mapping is bumping this rebuild cost up too much. If kj16v is as good as people say, then I may stick with the stock ECU and let him work his magic... if he were to say yes!

Sounds like a good guy! 8)