Boost on stock internals?

[Jbrown]

i have a 96 dodge neon sohc...switching to the dohc head and keeping the sohc block so it would lower my compression a little bit...and got the srt4 turbo setup.

well, how much boost should i run on stock internals? being that this is a daily driven car and has 160k miles..i dont want to be too hard on it. all the necessary fuel upgrades will be done with a wideband a/f...and a stage 1 clutch. for now, im only looking for 200-220whp.

planning on doing a 2.4 bottom end with srt internals soon though.

[turbovanman²]

I would say no more than about 5-6 psi. Any idea what your compression will be?

[Jbrown]

i believe stock compression on a dohc neon is around 9.5:1 the dohc head on my sohc block....im not sure about...but i know its a little lower

[turbovanman²]

If it is that high, definately stay around 5-6, you might be able to go more but of course, you have to listen for knock etc.

[Jbrown]

i asked a guy on one of the neon forums and he said around 8.3:1

[TurboGLH]

If that 8.3:1 is correct, your in decent shape. The problem that you still have is the weak rods and pistons in the motor, so your still going to be stuck with 5-6lbs if you want to be safe. A unit to watch knock as well as a wideband would be helpfull for you, but it will never be a real "safe" setup. Should be fun until your 2.4 swap though.

[turbovanman²]

i asked a guy on one of the neon forums and he said around 8.3:1


Well you could turn it up, we run 11 psi non intercooled on our 8 valves. I am not sure how well the rods will hold up.

[lbrmotorsports]

first off, if you put ojn a dohc head. it ups you compression, not lowers it. And you can run around 8 psi with no problems. Start off around 5 and work out any bugs the increase it. Many people around running 11psi on stock neons. Its all in the tuning, and remeber that you have higher compression beacuse of the dohc head!!!!!!!

[Jbrown]

why would it make higher compression if im keeping the sohc block? the dohc pistons in a neon are domed(hense more compression) and the sohc pistons are flat.the dohc has a high compression piston to make up for the larger combustion chamber, the dohc head on a sohc block will put you around 8.3-8.5 and the sohc head on a dohc block will give about 10.2 and both are posable.The SOHC head has higher compression than the DOHC head, but the DOHC pistons have higher compression than the SOHC pistons.

[tvanlant]

You are correct, putting the DOHC head on the SOHC engine will drop compression. Most of the people running the SRT-4 turbo setup on their DOHCs are running at MAX 10 psi. I just helped a guy do his turbo setup on his 98 R/T and he is running 6-8 psi to be on the safe side. Putting the DOHC head on your SOHC engine will NOT drop it to 8.3. It will drop it to around 9.2:1. That is low enough for around 10-12 psi to be safe. The stock internals are very weak, so it won't take much to break them.

[Jbrown]

i hear ya....thanks for the input..being that this is my only car right now and it has 160k miles on it...ill try to go easy on her and not hit boost every time i shift...but u know how u have those wanna be civic racers try you at a light and you get the urge to embarass them....:evil:

[Jbrown]

im gonna go ahead and do it right and rebuild the block with forged pistons/rods etc..its probably a good chance that an engine with 160+miles on it will be likely to blow within 20,000 miles after boosting it with stock internals..and dont feel like ripping it apart again

[TurboGLH]

Good call, it's a moderate-large investment but it'll pay off in both reliability and fun factor (no worrying if 8lbs vs 7lbs is going to be the death of your motor)

[moparzrule]

I know a guy with a GSR integra that runs 10 PSI on the stock longblock, they have well over 10:1 compression. And you guys are worried about detonation with 9.3:1 compression on 8 PSI??? I understand being worried about the shortblock strength because the rods espeically are weak on the SOHC engine, but there should be no detonation worries.
I've run 17 PSI non-intercooled on my log T1 before with 93 octane no issues.....mopar performance computer and 4.7V diode on the MAP. Only mod to add fuel was a squished FPR to give me 62-63 PSI base fuel pressure. No detonation, 1600 max EGT's and that was in it for awhile.