10:1 cr plus boost?

[boostinboy]

My buddy has an extra motor that came with his 92 tsi fwd he just picked up. The extra motor that i was thinking about grabbing off him is fully built with 10:1 compression forged pistons. I planned on putting this motor in my car and slapping on a 50 trim. Will this be safe and how much boost can/should i run? Btw, the reason he had a 10:1 cr motor built was because he had a n2o kit on it as well as boost

 

[liquordrunk]

first oof you wont be able to run no more than 15 psi im guessin maybe more without getting knock specially if ur on 93 or less octane high compression ratio mean more kncok on pump gas. that high of compression you spool that 50 full spool by 2700 there is no since in having compression that high unless you are draggin the car but it would spool a t77 like a mof fo

 

[boostedinaz]

You can run that motor, but it will be a bi*** to tune on pump gas. You will most likely have to run fairly low boost so that is wont detinate.

 

[DBR01]

^--I agree--^

 

[Lunch_Box]

PM swordfish, he is running a 2.4 with 10:1 compression.

 

[boostedinaz]

PM swordfish, he is running a 2.4 with 10:1 compression.

On pump gas??

 

[CanadianTalon]

A well tuned 10.0:1 engine at 12-14psi is just as fun as a "normal" setup at 18-19psi.

I agree there's a difference, but you're way overstating it. MM&FF did a test last month, comparing 8:1 and 12:1 on a race motor. The difference on 117 octane race gas was about 15% less power. That's a much larger spread than what you're talking about. Assuming the change in power remained the same for every amount of change in compression, you'll see about a 6.5% loss in power from 8.5:1 to 10:1 compression, or about 20 WHP on a 300 WHP setup. A couple pounds of boost, but not the 4-7 psi spread that you suggested. If by a typical setup you were comparing a 2.0 to your 2.4 I would agree, but not just on the compression difference. A honda tuner did a test similar to this, only comparing 9:1 to 10:1 compression. Spool was exactly the same between the two, and the higher comp motor made 12-14 WHP more power, on a 300 WHP setup.

 

[GreenStreak]

Yea I remember reading about swordfish's setup. He did use 93 octane, but he did mention how tuning was a real bi***.

 

[swordfish]

I usually run 101 in my car because we have it available at the pump here, but 19 psi on 91 octane is doable and I have done it. Less timing, more fuel, cold plugs and be damn sure it doesnt detonate. People will try to scare you about 10.0:1 setups but they are not that hard to tune if you take your time. The hardest part about tuning it is to be patient and forget everything you have ever learned about tuning lower compression setups. It can be a bit nerve racking at times but patience will pay off.

The thing about 10.0:1 setups is that there is little margin for error on pump gas so try not to make any mistakes. Make sure the tuning is dead on or get someone who is a great tuner to help you out. A well tuned 10.0:1 engine at 12-14psi is just as fun as a "normal" setup at 18-19psi. For fun, email Marco @ magnus sometime and ask him how much MPH he lost going from 10.0:1 to 8.5:1.

My car is driven every single day to work and where ever I have to go. It my personal transportation as I dont have a backup car other than my wifes car. My 10.0:1 2.4L Long Rod is reliable and a blast to drive. It runs just as well on pump as race gas I just cant run as much boost. But when I do have 91 octane in the car, it is running 17-19 psi. I prefer the 101 because its only $.80 more per gallon and I run 24-26 psi on it. On C16 the only think holding me back is the hacked 2G MAF. That will change this winter though.

Now if you are trying to tune this car with an AFC then forget 10.0:1. Get DSMLink at least or a stand alone. I run DSMLink w/ a hacked 2G MAF and it works great up to about 32 psi where things start getting scary with the VE map.

Hope that helps.

jeff

 

[boostinboy]

great, thanks alot guys, u made my desicion a lot easier, i think im just gonna run 10psi with an Safc when i get the motor installed just to play it safe untill i can afford to go stand alone. Hmmm what size injectors should i get for my 50 trim @ 10 psi????

 

[laggin3]

jeff

Man I was so going to jump your ass for not updating the site, but I just checked it. What is your offset on the wheels?

 

[swordfish]

Yeah I'm a bit slow sometimes with the updates.

The offset for my wheels are 45mm offset but I machined a cool set of 5mm spacers out of billet for a total of 40mm.

jeff