[ICEMAN99TURBO]

Not sure if this has been talked about before but I thought I would bring it up since I haven't noticed anything on it.

Guess this could go for Boosted 6G72s as well....

Here is the convo.. In a project boost thread on TGC.

I dunno man, I have always been taught if you want to boost, you run low compression or things will detonate. Inless you plan on running like 3/4 PSI. Again, what fun is boost if you can't feel it hold you in your seat? I always saw that (for me) perfect bost was around 20/25 PSI.

Guess I will see her when she is done.

You want to run the highest compression you possibly can. An 8:1 4 cyl would have zero fucking power/tq until boost came on which would suck to drive around. Run higher compression, higher octane, and less boost. "the lower the compression the better" school of thought is wayyyy outdated.

Perfect level of boost? You set a power goal and do what you have to in order to achieve it. With higher flowing parts (intake main/heads/exhaust etc) you need less boost to make the same amount of power. Or just keep stock parts on there and run 30lbs for ricer bragging rights. Unhooking your wastegate will help get you there.

Is the thought way outdated?

 

[Bitter]

its all in the tuning when running boost with higher CR. the low cr and high boost is good for making big numbers, but yea sucks for actually driving around. a well rounded machine it is not. drive an evo out of boost, its horrid. this is why people twin charge, to compensate the low cr with boost all the time. but for daily use/tracking keeping a higher CR to make good power off boost is best.

 

[ICEMAN99TURBO]

its all in the tuning when running boost with higher CR. the low cr and high boost is good for making big numbers, but yea sucks for actually driving around. a well rounded machine it is not. drive an evo out of boost, its horrid. this is why people twin charge, to compensate the low cr with boost all the time. but for daily use/tracking keeping a higher CR to make good power off boost is best.

I was hopeing to see you post. :wub:

So, ok just for instance, say I have a friend who had a 03 GTS with an SDS.. and it blew/never ran right. The GTS 3Gs run 10:1 compression and was thought (or maybe it was just me who thought) they were not strong enough to handle boost well. Was this the fault of the internals, the whole motor, the tunning, or just the idea idea that "you can't boost higher CR motors" that was wrong?

:edit:
I guess I actually know the answer, it is just that I must be green still with the whole boost idea cause I thought that the higher the PSI on a higher CR motor, the more issues you would have.

 

[Bitter]

gts pistons are weaksauce. good forged 10:1 pistons with a good tune will run boost all day long. people boost the engine in my celi with 5-8psi on the stock 11.5:1 pistons. they're good till the 220whp range. the gts pistons are just not able to handle anymore than a stock engine. i'd bet an agressive NA tune would break them.

 

[ICEMAN99TURBO]

gts pistons are weaksauce. good forged 10:1 pistons with a good tune will run boost all day long. people boost the engine in my celi with 5-8psi on the stock 11.5:1 pistons. they're good till the 220whp range. the gts pistons are just not able to handle anymore than a stock engine. i'd bet an agressive NA tune would break them.

So, in a way, any compression will run a decient amount a boost as long as the internals are up to par.?. :agreed:

 

[Black_out]

I know at least 4 guys on RDtiburon.com running anywhere from 17 all the way up to 22psi on daily driven 2.0L beta engines with completely stock internals. The only thing done to them internally is 3 of the 4 swapped to the 1.8L intake came because it's a little more aggressive. The guy running 22lbs has daily driven it for the past 2 years for sure without any problems.

 

[Bitter]

So, in a way, any compression will run a decient amount a boost as long as the internals are up to par.?. :agreed:

yea, but there is a limit. you don't go cramming 10psi down an engine with 13:1 CR. well actually you could, but you need some beefy shit.

 

[ICEMAN99TURBO]

I know at least 4 guys on RDtiburon.com running anywhere from 17 all the way up to 22psi on daily driven 2.0L beta engines with completely stock internals. The only thing done to them internally is 3 of the 4 swapped to the 1.8L intake came because it's a little more aggressive. The guy running 22lbs has daily driven it for the past 2 years for sure without any problems.

Yea, but what is the compression rate?

yea, but there is a limit. you don't go cramming 10psi down an engine with 13:1 CR. well actually you could, but you need some beefy shit.

Ohh, I know. I know that you have to give and take. Like i figured with the 10:1 for the GTS you could only run about a 5-6 PSI before you start breaking shit.... on OEM internals, but maybe that is too much with OEMs. :lol:

 

[Black_out]

Completely forgot to put that. If I remember right 11.1:1. I'll go check though because that doesn't sound completely right.

 

[Black_out]

10:1.

 

[ICEMAN99TURBO]

Also, inline motors would handle the boost better than the V motors, so maybe that would help with the higher compression rates as well?

 

[Bitter]

you could build a 6g72 with 10:1 CR to run enough boost to make your WHP goals. the benefit is you get to run a smaller turbo which spools faster or a smaller supercharger which draws less power and end up making the same power. but you have less room to grow. you build to meet a power level, not build and then see how much it can make.

 

[ICEMAN99TURBO]

you could build a 6g72 with 10:1 CR to run enough boost to make your WHP goals. the benefit is you get to run a smaller turbo which spools faster or a smaller supercharger which draws less power and end up making the same power. but you have less room to grow. you build to meet a power level, not build and then see how much it can make.

Build with a plan, not a goal.. got yea. Thank you for the lesson. We should live closer. :lol:

 

[2000RS-Turbo]

Im gonna go 9:1 for three reasons, Ill have more room to run more boost (making more power), i dont wanna have to run race gas and dont have e85, 9:1 is more forgiveable if something goes wrong say the vac line blows off the wastegate and i spike really high less change of having damage

 

[ICEMAN99TURBO]

Im gonna go 9:1 for three reasons, Ill have more room to run more boost (making more power), i dont wanna have to run race gas and dont have e85, 9:1 is more forgiveable if something goes wrong say the vac line blows off the wastegate and i spike really high less change of having damage

I could be wrong, but I beleive that is what my (the) Fed GT runs OEM.. What do the OEM GS/RSs run, 9:1?

 

[Bitter]

I could be wrong, but I beleive that is what my (the) Fed GT runs OEM.. What do the OEM GS/RSs run, 9:1?

yes, but stock pistons are cast and weak. wimpy wimpy wimpy, you need forged and strong. hefty hefty hefty!

 

[ICEMAN99TURBO]

yes, but stock pistons are cast and weak. wimpy wimpy wimpy, you need forged and strong. hefty hefty hefty!

:lol: I love how you put things my friend.

 

[MattS00]

I would like to add a little bit here, and try to make it as short as I can, but still understandable for those that don't have a lot of experience.

There is more to it that just the static compression ratio of the pistons. A lot of it has to do with detonation resistance of the enginewhich is really tied to the burn rate of the combustion chamber. The shape of the combustion chamber has everything to do with the burn rate. i.e. head chamber volume/shape, piston squish (quench) area, and how the air flows into the combustion chamber. The faster the burn rate and the better the air/fuel charge is mixed the detonation resistance increases. With a faster burn rate chamber you can use less timing for a set power goal, so the VE increases because of less pumping losses. The lower timing also reduces the chance of detonation.

Another important factor is the heads ability to wick heat away from the combustion chamber. Hot spots can cause detonation, and over expansion of components. Both will lead to severe engine damage.

Also, worth noting is effective compression ratio. The compression test numbers of a big cam motor vs a stock cam motor with the same pistons will be lower. The bigger cam will loose low end power, but will allow the engine to breath better at high RPM. This is very similar to lowering the compression ratio with dished pistons or a thicker head gasket, but with the added benefit of better VE at higher RPM. The lower effective compression ratio doesn't compress the charge as much, so you can run more boost before detonation starts to occur, which more than makes up for the loss in compression. Also, a bigger cam can leave more exhaust in the combustion chamber after the exhaust stroke. This is actually a good thing. If the exhaust is mixed into the incoming air/fuel charge, it actually lessens the chance of detonation by effectively increasing the octane rating of the fuel. This is similar to methanol/water injection.

There are a lot of different factors that play a role in making power, and finding the right balance for the engine you are working on is the difficult part.

 

[Bitter]

I would like to add a little bit here, and try to make it as short as I can, but still understandable for those that don't have a lot of experience.

There is more to it that just the static compression ratio of the pistons. A lot of it has to do with detonation resistance of the enginewhich is really tied to the burn rate of the combustion chamber. The shape of the combustion chamber has everything to do with the burn rate. i.e. head chamber volume/shape, piston squish (quench) area, and how the air flows into the combustion chamber. The faster the burn rate and the better the air/fuel charge is mixed the detonation resistance increases. With a faster burn rate chamber you can use less timing for a set power goal, so the VE increases because of less pumping losses. The lower timing also reduces the chance of detonation.

Another important factor is the heads ability to wick heat away from the combustion chamber. Hot spots can cause detonation, and over expansion of components. Both will lead to severe engine damage.

Also, worth noting is effective compression ratio. The compression test numbers of a big cam motor vs a stock cam motor with the same pistons will be lower. The bigger cam will loose low end power, but will allow the engine to breath better at high RPM. This is very similar to lowering the compression ratio with dished pistons or a thicker head gasket, but with the added benefit of better VE at higher RPM. The lower effective compression ratio doesn't compress the charge as much, so you can run more boost before detonation starts to occur, which more than makes up for the loss in compression. Also, a bigger cam can leave more exhaust in the combustion chamber after the exhaust stroke. This is actually a good thing. If the exhaust is mixed into the incoming air/fuel charge, it actually lessens the chance of detonation by effectively increasing the octane rating of the fuel. This is similar to methanol/water injection.

There are a lot of different factors that play a role in making power, and finding the right balance for the engine you are working on is the difficult part.

hit the nail on the head, but i was just trying to keep it very very simple. every engine is different, don't try to run high comp on a slant6 and expect to get very far. :lol:

 

[catch-me]

Jeremy don't you know how to post in the right section :lol: jk I will admit that this thread does have good info for us 4 banger guys too.