i have a decompression plate...but was wondering would i be able to obtain 230-250whp without one..cause thats basically all im looking for....and with one what am i looking for max hp..i guess basically im asking what is the max hp usually seen safely without lowering compression and what is the max with lowering compression via decompression plate

any info would be greatly appreciated

thanks

 

Have you read Maximum Boost yet? It has a graph showing maximum allowable boost PSI for every compression ratio and for a couple of different octane fuels (page 155). I think we have 10.3:1 compression ratio. For that ratio and 92 octane fuel, the graph shows at most about 3 psi. For 100 octane fuel, it shows about 7 psi. For 120 octane fuel, it shows about 12 psi. I'm sure these figures are not set in stone, but they should give you some idea. You probably need around 10 psi, so eyballing the 10 psi at 10.3:1 compression ratio, I would say you need at least 110 octane (which i don't think is achievable even with premium fuel and octane additives).

On a side note, the author also says that decompression plates are a bad method to decrease compression ratio.. although people seem to have success with them.

PS haha I just realized the book is called Maximum Boost and the graph shows maximum boost levels smile.gif)

 

do some searching. We have a user on this forum who is running 270whp with no internal engine work and hasn't had any issues. His dyno is in the horse power thread

 

The numbers given in the book are very conservative I guess. But I think that JonGTR's setup was just sort of an experiment and I don't know how reliable it was (or for how long he ran it). It also was tuned great, AFR never went over 13.5.

 

yeah, i think jon is still running his setup, and it was VERY reliable.. yeah, tuning is what you need to have done the best about the WHOLE turbo setup..

you can push 230-250 very safely on stock compression and all stock motor, it just needs to be tuned correctly.

maximum boost is just a general idea for everything, its different for each motor or setup..

decompression plates arent really BAD by no means, i just wouldn't try pushing 400whp with one.. i would only use one if you are worried about wanting lower compression so you can push more boost, but at those horsepower levels the only point for a decomp. plate would be to give you a sense of security.

 

I have sort of a related question.. If you can run about 10psi boost with stock compression with no detonation, does that mean you would be able to run a NA setup with higher compression (say 15:1) and no detonation? Would that help a NA setup make more power?

 

no idea.. lol i no nothing about N/A and higher compression. fing02.gif

why would you want to run such a high compression anyway?

for boost, like i said earlier, its all in the tuning.. if your car is tuned crappy, im sure you will be detonating at 10psi..

 

so for 230-250 whp..i should be ok without the decompression plate?

 

 

haha.gif haha.gif haha.gif sometimes even the MOST obvious needs to be pointed out AGAIN, after its spelled out for someone. nana.gif