Question on High compression motors

asanti · Post by **asanti** » Wed Aug 13, 2008 12:46 pm

How will a hi-compression motor affect emissions? For those of you that have either 10.5:1 or 11.0:1 motors, will the NOx emmissions skyrocket? I'm asking because in CT we have to go through emmissions and I'd hate to build the block then get stuck w/ a car that won't pass emmissions here

. Oh, and before anyone mentions MS, this is for my DD so MS is out until I get a replacement vehicle....SOMEDAY

Thanks in advance for any pointers I should look out for before diving head first into this!

Later
Allex

Post by **racer12306** » Wed Aug 13, 2008 8:28 pm

Raising compression ratio will increase the effiency of the burn when it ignites.

Thus, imo, if you can properly tune the mixture you should be fine in regards to emissions.

excon · Post by **excon** » Wed Aug 13, 2008 8:40 pm

Hate to thread jack but...

Would you need to use MS on our cars to run higher compression? Our cars already run rich...

MoxHair · Post by **MoxHair** » Wed Aug 13, 2008 10:09 pm

I dont think anyone has raised the compression on a 03+ Neon, so how the New Style computer reacts is anyones guess. I would think MS would be a must, but who knows. You'll def have to switch to 93octane, with higher compression comes higher temps and detonation is a sumbitch.

Post by **racer12306** » Wed Aug 13, 2008 10:28 pm

He has an 01, he's just switching the rear to an 03

asanti · Post by **asanti** » Thu Aug 14, 2008 10:25 am

MoxHair Posted: Wed Aug 13, 2008 10:09 pm Post subject:

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I dont think anyone has raised the compression on a 03+ Neon, so how the New Style computer reacts is anyones guess. I would think MS would be a must, but who knows. You'll def have to switch to 93octane, with higher compression comes higher temps and detonation is a sumbitch.

Well to eliminate any confusion, I have an '01 with the standard 9.8:1 compression already (Cali emissions flattop pistons). I'm banking on getting DOHC 10.5:1 pistons in the SOHC block which SHOULD get me close to 11.0:1

. I've an AF/X-R already and there's a SAFC Neo waiting to be installed too; 93 octane has been the norm for me for quite a while now

and detonation should be kept in check with those two keeping an eye on fuel trims + all the other neat things the Neo does.

racer12306 Posted: Wed Aug 13, 2008 10:28 pm Post subject:

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He has an 01, he's just switching the rear to an 03

Good eye!

Sigh, the things I do just to get the damn Mopar lip kit on...

.

Thanks guys!
Allex

MoxHair · Post by **MoxHair** » Thu Aug 14, 2008 5:31 pm

and you guys are both tools because the guy who posted above me drives an 03 and i was answering his question.

bone-yard-racing · Post by **bone-yard-racing** » Thu Aug 14, 2008 5:39 pm

Cali emissions pistons are dished and give about 9.3:1 FYI you have regular SOHC pistons flat 9.8:1
DOHC high comp pistons will more than likely hit the head why not just get high comp SOHCs

asanti · Post by **asanti** » Fri Aug 15, 2008 9:31 pm

bone-yard-racing Posted: Thu Aug 14, 2008 5:39 pm Post subject:

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Cali emissions pistons are dished and give about 9.3:1 FYI you have regular SOHC pistons flat 9.8:1
DOHC high comp pistons will more than likely hit the head why not just get high comp SOHCs

Well then the dealer sticker lied since it said the car had the Cali emissions package, but my piston tops are flat, go figure. Aside from that I was led to believe using DOHC pistons would get me to 11.0:1 vs the 10.5:1 with domed SOHC pistons. If that's bad info then someone shed light on this for me?

Later
Allex

Post by **occasional demons** » Sat Aug 16, 2008 12:22 am

03blackrt wrote:DOHC pistons + 0.030" head milling + SOHC cylinder head + standard bore = ~10.86:1 CR

asanti · Post by **asanti** » Sat Aug 16, 2008 4:58 pm

occasional demons wrote:
03blackrt wrote:DOHC pistons + 0.030" head milling + SOHC cylinder head + standard bore = ~10.86:1 CR

Hmm interesting... Now what if I were to get the pistons .020 over and of course have the block machined .020 over?? Would that make any difference in CR?

Thanks
Allex