[Mk2] [Turbo] Compression ratios and head gaskets

[kev8611]

What thickness are the standard Rev 3 headgaskets? I thought they were just under 1.1mm

Sorry. 1.3mm

[bobhatton]

Trickster - it did happen and it happened lol.

1.2 bar, st205cc and a hybrid CT20 to be precise.

I should point out though that the car has done a fair few track miles and a few flat out runs where ive touch the rev limiter in 5th gear.

So a hard life lol.

A Rev 3 is safer than a Rev 1,2 at that boost because Toyota knew what they were doing and lowered the compression ratio down from 8.8:1 to 8.5:1 when they raised the boost.
Now why would they do that small change if compression ratio does not matter, it’s because it does, even that small amount if you want to get the best out of the boost being run.
If anyone understands how engines work they know the ignition timing needs to stay as designed and if the boost is being raised on the same fuel the compression ratio has to be lowered.

All the MR2 Turbo engine running in this country with stock ECU are all working under the control of the knock sensor. But that can only do so much and in the end the head gasket will blow or the ring land break under detonation.

[MR2 Rich]

Trickster - it did happen and it happened lol.

1.2 bar, st205cc and a hybrid CT20 to be precise.

I should point out though that the car has done a fair few track miles and a few flat out runs where ive touch the rev limiter in 5th gear.

So a hard life lol.

A Rev 3 is safer than a Rev 1,2 at that boost because Toyota knew what they were doing and lowered the compression ratio down from 8.8:1 to 8.5:1 when they raised the boost.
Now why would they do that small change if compression ratio does not matter, it’s because it does, even that small amount if you want to get the best out of the boost being run.
If anyone understands how engines work they know the ignition timing needs to stay as designed and if the boost is being raised on the same fuel the compression ratio has to be lowered.

All the MR2 Turbo engine running in this country with stock ECU are all working under the control of the knock sensor. But that can only do so much and in the end the head gasket will blow or the ring land break under detonation.

But what if these ticking time bomb engines you always talk off have uprated intercoolers?

So Bob a stock engine running stock boost on 99 ron- what should the compression ration be?

What is the compression ration for a 500 bhp engine generally speaking?

[jimGTS]

i have to say i have noticed timing being pulled when ive forgot to use my water injection.

requires an ecu reset and the difference is noticeable.

i choose not to go down the road of aftermarket ecus this time around, (to save time/money/headache), i rather like the OEM ecu taking care of things.

many aftermarket ecus dont pull timing when it senses knock unlike the OEM ecu, which is surely a good thing?


question is, is there way a of getting around this issue WITHOUT having to rebuild and go even lower compression??

get an ecu mapped for say 97 ron fuel and run 99?
run less boost?
run a more efficient turbo?
run water/meth injection?
rebuild engine?

i would have thought with some good cooling, water injection, stable/increased fuel pessure; a gen3 turbo should be able to run 350+hp all day long on the oem fuel system and ecu with the right turbo?

ryanRS made over 400hp on 540s, granted on a 2.2.

[bobhatton]

Trickster - it did happen and it happened lol.

1.2 bar, st205cc and a hybrid CT20 to be precise.

I should point out though that the car has done a fair few track miles and a few flat out runs where ive touch the rev limiter in 5th gear.

So a hard life lol.

A Rev 3 is safer than a Rev 1,2 at that boost because Toyota knew what they were doing and lowered the compression ratio down from 8.8:1 to 8.5:1 when they raised the boost.
Now why would they do that small change if compression ratio does not matter, it’s because it does, even that small amount if you want to get the best out of the boost being run.
If anyone understands how engines work they know the ignition timing needs to stay as designed and if the boost is being raised on the same fuel the compression ratio has to be lowered.

All the MR2 Turbo engine running in this country with stock ECU are all working under the control of the knock sensor. But that can only do so much and in the end the head gasket will blow or the ring land break under detonation.

But what if these ticking time bomb engines you always talk off have uprated intercoolers?

So Bob a stock engine running stock boost on 99 ron- what should the compression ration be?

What is the compression ration for a 500 bhp engine generally speaking?

Uprated intercooler, tell me how you think that will help please.

Stock JDM engine with our fuel 8.3:1 should do it but 8.0:1 will be just as good.

For a 500 hp engine the comp could be anything from 6.0:1 to 14.0:1 depending on the engine design and fuel used

[MR2 Rich]

Trickster - it did happen and it happened lol.

1.2 bar, st205cc and a hybrid CT20 to be precise.

I should point out though that the car has done a fair few track miles and a few flat out runs where ive touch the rev limiter in 5th gear.

So a hard life lol.

All the MR2 Turbo engine running in this country with stock ECU are all working under the control of the knock sensor. But that can only do so much and in the end the head gasket will blow or the ring land break under detonation.

How do you know they are all running on the knock sensor?

[MR2 Rich]

A Rev 3 is safer than a Rev 1,2 at that boost because Toyota knew what they were doing and lowered the compression ratio down from 8.8:1 to 8.5:1 when they raised the boost.
Now why would they do that small change if compression ratio does not matter, it’s because it does, even that small amount if you want to get the best out of the boost being run.
If anyone understands how engines work they know the ignition timing needs to stay as designed and if the boost is being raised on the same fuel the compression ratio has to be lowered.

All the MR2 Turbo engine running in this country with stock ECU are all working under the control of the knock sensor. But that can only do so much and in the end the head gasket will blow or the ring land break under detonation.

But what if these ticking time bomb engines you always talk off have uprated intercoolers?

So Bob a stock engine running stock boost on 99 ron- what should the compression ration be?

What is the compression ration for a 500 bhp engine generally speaking?

Uprated intercooler, tell me how you think that will help please.

Stock JDM engine with our fuel 8.3:1 should do it but 8.0:1 will be just as good.

For a 500 hp engine the comp could be anything from 6.0:1 to 14.0:1 depending on the engine design and fuel used

So colder air doesn't prevent knock?

[bobhatton]

Would you care to explain how cold air will prevent knock.

[bobhatton]

How do you know they are all running on the knock sensor?

Because by adding high octane fuel or installing lower compression pistons the engines then start to perform the way they should do, See jimGTS post above.

[MR2 Rich]

How do you know they are all running on the knock sensor?

Because by adding high octane fuel or installing lower compression pistons the engines then start to perform the way they should do, See jimGTS post above.

Ok, so no physical evidence?...

[MR2 Rich]

Would you care to explain how cold air will prevent knock.

So for the uneducated, what does cooler intake air from an uprated intercooler do?

[Marf]

For an engine running compression too high for the fuel it's using? Increase the likelihood of knock probably.

[kev8611]

Surely if the air charge is too hot the fuel will evaporate or pre-det which would cause knock?

[Marf]

Surely if the air charge is too hot the fuel will evaporate or pre-det which would cause knock?

It'd have to be pretty damned hot to do that!!

[bobhatton]

Would you care to explain how cold air will prevent knock.

So for the undereducated, what does cooler intake air from an uprated intercooler do?

That is what I am asking you to explain please.

[gavinda]

in regards to engine knock,preignition. The cooler intake air lowers in
cylinder gas temperatures at the end of the compression stroke. Reducing the
gas temperature at the end of a compression stroke reduces knock.

what were your intake air temps on track? chargecoolers tend to be less effective for longer durations of wide open throttle depending on if the system is large enough.

[MR2 Rich]

How do you know they are all running on the knock sensor?

Because by adding high octane fuel or installing lower compression pistons the engines then start to perform the way they should do, See jimGTS post above.

Still waiting for some evidence that lowering the compression ratio makes a engine perform better...

[Peter Gidden]

How do you know they are all running on the knock sensor?

Because by adding high octane fuel or installing lower compression pistons the engines then start to perform the way they should do, See jimGTS post above.

Still waiting for some evidence that lowering the compression ratio makes a engine perform better...

What do you mean by evidence?

Will Garrett's word do?

http://www.turbobygarrett.com/turbobyga ... with_boost

[ashley]

How do you know they are all running on the knock sensor?

Because by adding high octane fuel or installing lower compression pistons the engines then start to perform the way they should do, See jimGTS post above.

Still waiting for some evidence that lowering the compression ratio makes a engine perform better...

Why not go and do some research for yourself, plenty written on the subject and lots and lots to learn from

To name a few:

http://www.amazon.com/Maximum-Boost-Tur ... 22-4602015

http://www.amazon.com/Four-Stroke-Perfo ... ine+tuning

http://www.amazon.com/Induction-Perform ... 997&sr=1-3

[ashley]

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