how can I get more psi out of a turbo gsr ??

I have read that that safest psi for a gsr is only about 8 . what kind of work would I need to do to get about 12 -15 psi out of it ?

forged rods/pistons amnd dropping the compression while you do it, maybe around the low 9.?'s:1.
not sure if yuod have to sleeve it as well but for 12 if you had forged internals and lower cr I doubt it.

Contrary to popular belief, lowering compression isn't the greatest idea if you can avoid it. Your engine will suffer more lag and have far less power when not in boost.

The reason to lower compression is so that the engine will be safer when tuning is not up to snuff. Save up for a standalone engine management system and you will be thankful that you waited. A finely tuned standalone with stock compression (or even higher) can be just as reliable as a low compression engine with a mediocre tune.

What you need to safely up the boost is a very personal decision. You will get all kinds of responses on what people consider "safe". My definition of safe means; well-tuned and retuned 2-4 times a year, bullet-proof daily reliability when maintence is up to date, occasional track use, 80K+ engine life.

To meet my standards I have come to the conclusion that 10-12psi requires standalone engine management (no decompression), forged pistions and rods, and a block guard. The weakest part is the block guard.

Above 12psi I'd recommend a resleeve instead of a block guard. I'd be willing to run 18psi daily with the parts listed above and an 84.5mm GE resleeve in place of a block guard.

ok,well, even being tuned right, on his stock internals, they are only going to handle so much pressure, even tuned right. and of course you need to tune it right, i just didnt ad that cuz I figured jhe was only worried about what kind of engine work he needed to do. theres fuel you gotta worry about as well, along with other things but I wasnt focused on those. but on lower cr you can have more boost. eventually though you could go too low and not have any torque to get yopu moving and spool the turbine, but 9:5 should be fine, but thats just my oppinion.

Contrary to what you read on most forums, there is no need to decrease compression any time you boost the engine. And contrary to this forum, the GSR can handle just as much boost in stock form that an LS can. I'm guessing that the "LS can handle more boost" idea is stemming from the compression issue, but it is false.

Assuming good tuning, there is no advantage to running lower compression. An engine's maximum capacity is a dynamic compression number. In very basic terms, dynamic compression is a combination of the static compression and the pressure of the inlet air. There is no reason to decrease static compression just to make up for it with inlet air pressure. That will just cause less off-boost power.

im guessing why the LS is said to handle more boost is because, like me, probably not alot of people here know what in the hell you are talking about! :eek7:


:biggrin:

I understand that. FWIW, static cr is just the volume of a cylindar when the piston is at bottom dead center (all the way down). Dynamic cr is that same volume adjusted for altitude/air density and the loss of air because the intake valves aren't all the way closed when the piston starts to compress. For the LS, scr is 9.2:1 and dcr is 8.0:1.

Also, just for the sake of correct information... The GSR will have more dynamic compression when boosting the same amount as an LS because it has higher static compression. The reasons it can handle that extra boost are the better rod ratio that doesn't put as much stress on the cylindar walls and the oil squirters that cool down the pistons a little bit which can help fight detonation.


I'm sorry if that's too technical. I'll be more than happy to explain something if you're still curious.

I understand that. FWIW, static cr is just the volume of a cylindar when the piston is at bottom dead center (all the way down). Dynamic cr is that same volume adjusted for altitude/air density and the loss of air because the intake valves aren't all the way closed when the piston starts to compress. For the LS, scr is 9.2:1 and dcr is 8.0:1.

Also, just for the sake of correct information... The GSR will have more dynamic compression when boosting the same amount as an LS because it has higher static compression. The reasons it can handle that extra boost are the better rod ratio that doesn't put as much stress on the cylindar walls and the oil squirters that cool down the pistons a little bit which can help fight detonation.


I'm sorry if that's too technical. I'll be more than happy to explain something if you're still curious.

a little technical . So let me get this straight , gsr's can handle the same amount of boost as ls's can, safely ?? I was told that the v-tec head couldnt handle the boost or somethin , I definately want to keep the v-tec head onn , that shit is addictive !!

the only thing ive heard of vtec not going well with boost was that on the vtec lobes you have alot of valve overlap which lets some boost bleed off. and your description wasnt too technical, I just wouldnt know how to figure that thing out. do you have an equation or anything?

Here's the calculator that I use...
http://www.rbracing-rsr.com/comprAdvHD.htm
If you need the specs on your engine give the the exact engine code and I'll get them.

The VTEC head design is much better than the LS. Not only does it flow better, but the way that the rocker arm assemblies connect is much better for higher rotations. It does bleed off more pressure in VTEC due to the overlap, but some of that can be corrected with cam gears. It's also a good safety measure to not have quite as much dynamic compression as the rpms climb. That may be part of the reason for being able to handle the boost, although that's a guess on my part.

7-8 is safe on a GSR. It doesn't "require" good tuning, but as I've said earlier... As far as I'm concerned your engine will live or die on its tuning.

Another nice point for the B18C1 is that at pretty much any boost level it will make roughly 40-50 more whp than its LS counterpart.