10.5:1 or 11:1 compression

[svtrickey]

What's a safe amount of boost on a 10.5 or 11:1 compression motor? I have a meth kit and will be running 93. And then 107 and meth at the track.

I was thinking about going built and D1sc with 10-12psi. This should give me great low end and still a killer top end.

I know most run 8.5-9:1 on boosted motor but I don't pull boost every day and only put 3-7k on the cobra a year. I am just thinking outside the box and norm. I know it's way safer to run 9:1 but I don't see why it's such a big problem to run 11:1 and 12lbs.

What are your thoughts? And has anyone tried this before if so what did you make and how did it run?

96 mystic: 01 ported intake, 5.0l mmr Stroker, 03 p&p heads, comp 2 blower cams, power pipe, 4:30 gears, DET locker, 335 meats, SHM headers, dr. Gas x pipe, svo side exhaust, mm k-member and coil overs, and grip package for the rear, d1sc 10-12psi on 10.5 or 11:1 compression.

What kind of times should I run with that setup? And what kind of power?

 

[PSUCOBRA96]

9.1 is a bit safer but the real reason is that people can throw much higher boost numbers at it. It seams tuners are getting better and better and compression ratios are going up. 10.1 may be a good compromise. A bit above stock but not too much. or just go 10.5 and get a good tune.

 

[Blown_By_You]

I'd stay 10.5, which is high, but I wouldn't be worried about it.. It drives me crazy how people are so afraid of compression with forced induction. Centrifiguls don't produce a lot of cylinder pressure low in the powerband, where the higher compression would really be hurting you due to dwell time, as opposed to an eaton or twinscrew car. The higher compression will just help with responsiveness down low and won't hurt you a bit up top.

 

[pacific4v]

Is ethanol an option as a fuel? I already have a similar setup on ethanol as a fuel. 11:1 5.0 stroker with an intercooled s-trim. Stock h/c/i too. I made 515rwhp/505 tq at 5600rpm making 9.5psi. I had some maf problems so that was as high as it could rev until its fixed. That number was on 18° timing(low for e85) and rich. I expect 11-12 psi once i retune it and 600rwhp. You may want to rethink those 4.30s too. I had them with the blower and blew the tires off at the top of 3rd and sometimes 4th too.

 

[svtrickey]

Dwell time? And I agree, my tuner said run 11:1 and meth and 12lbs. I don't understand why people don't run this combo more. I know you can always throw more boost at it to make more power if you run low compression but your putting a lot of wear on the parts with higher boost too. So run 10-12 and 11:1 and you should have a very fast car and not a lot of wear as I don't pull boost every wear I go. I haven't hit boost in my lightning in 6 months.

 

[svtrickey]

Is ethanol an option as a fuel? I already have a similar setup on ethanol as a fuel. 11:1 5.0 stroker with an intercooled s-trim. Stock h/c/i too. I made 515rwhp/505 tq at 5600rpm making 9.5psi. I had some maf problems so that was as high as it could rev until its fixed. That number was on 18° timing(low for e85) and rich. I expect 11-12 psi once i retune it and 600rwhp. You may want to rethink those 4.30s too. I had them with the blower and blew the tires off at the top of 3rd and sometimes 4th too.

See this is the info I am looking for! Thanks I am going to try the 4:30's and see what happens. I am going to run 345/35/18 and MT et streets. The car doesn't see the road but on nice days so I am hoping that will help me hook.

 

[svtrickey]

Ethanol is not an option. There is like 1 station about 25miles away from me. I don't mind the 93 and meth. Might just run 100 which is very close to me.

 

[STAMPEDE3]

It drives me crazy how people are so afraid of compression with forced induction.

^^^This

 

[IOWA]

I'm running a 10:1 Aluminator motor, with 11psi of boost. Also running Meth spraying constant over 2psi of boost. With stock heads/cams, it put down 485 at the wheels on 93 Octane fuel.

 

[SpittingCobra]

Is the engine already built? Did they cc your chambers yet? I'm asking because my new engine has stock stroke, Manley flat tops, ported heads. After the chamber work done on the heads, the compression ended up at, guess what.. 9.85:1 lol. So it might not be as high compression as what your guesswork is giving you. All depends on the gasket thickness, chamber work, piston depth.

If it's already built and spec'd at 11:1 then disregard. Just throwing it out there since you were between 10.5/11 on your question.

Should be a good setup either way good luck with it.

I'm running the D1sc as well, heard it runs a lot better within the 15+ psi range so I was hoping to be able to run around with a 3" or so pulley on mine all the time.. we'll see if that works out with octane etc. Was running a 3.8" on the stock engine seeing 10psi peak out of it, only lasted about a year..

 

[NoviGT2000]

I have a novi 2000 and if i decide to keep the car and upgrade some things I will be upping the compression to 10.5.1. You will make serious power and have no issues. If your tuner knows how to tune for high compression motor you will have no problems. I have seen two cars with high compression motors on high boost run insane times and make serious power and still drive them on the streets to tell the tale. Do a little research on higher compression and higher boost. You will find the results to be interesting and possibly worth that added compression.

 

[svtrickey]

Thank you everyone for getting back to me. The motor is getting built as we speak was just unsure of what compression I wanted to run. It will be 11:1, and I have a great tuner. I will be going for a super safe tune and nothing wild.


Any guess on power and 1/4 times?

I'll be updating as I go along, but ill start a new thread for that.

 

[Noreast]

Good move!! Im around 10.5-1 compression all i want is around 400rwhp so with low boost i can be there easily. Cant imagine 10psi+!! Gunna be a sick car for sure! Post up some pics of the build if you could, always love following sick builds lol