Compression Ratio, octane and boost

[matt texass]

Let me see if I got this straight. It is bad to run 15-16# on (93) because that is to little octane for boost and compression that is to high. The terminator guys get away with it because they have a descent motor that doesn't have toothbrush rods and have an 8.5:1 compression ratio. So what is the approximate max boost to run with 93 on an aluminator with 8.7:1 compression?

 

[CataclysmGT]

I'd just like to point out that my little stock Mitsu Evo is pushing 20+ psi 9.0 CR on 91 octane.
There are guys with modded Evo's pushing 24psi on 91 octane....
93 with an aluminator...run lots of boost!!!

 

[DirtyDogOfTheDesert]

There are a lot more factors than just the three mentioned. Timing, IAT's, Camshaft, etc.....
I run 18psi on 94 octane pump gas with 9.6:1 motor, and it's been working great since I got tuned by a "competent" tuner.

 

[matt texass]

Ya I thought I remember 05 stroker was pushing somewhere around 20# but I don't know if that was on pump or what his comp. ratio is.

 

[05stroker]

Ya I thought I remember 05 stroker was pushing somewhere around 20# but I don't know if that was on pump or what his comp. ratio is.

I Have made 20 psi on 93 but I like 15 psi on pump and race fuel after that , main reson for that is my setup lovvvvves timing and makes great gains when timing can be raised.The only way to run 20 + psi and 23 or 25 deg of timing is on race fuel , at least with my setup .

 

[matt texass]

I Have made 20 psi on 93 but I like 15 psi on pump and race fuel after that , main reson for that is my setup lovvvvves timing and makes great gains when timing can be raised.The only way to run 20 + psi and 23 or 25 deg of timing is on race fuel , at least with my setup .

What is the boost "window" with the F1? Where do you need it? What is your comp. ratio?

 

[05stroker]

What is the boost "window" with the F1? Where do you need it? What is your comp. ratio?

Mine is 9.0:1 and 15 psi is a min that I think the F1 likes , from there on I think is works very well . They say it will do 30 psi . I even thought about ( and still am ) about running the same pulley as the race tune and just setting the tune to shift earlier (maybe 5600-5800) to keep the boost down. Either that or a high boost low timing setup for the street. That way I dont have to change anything but the tune . With the new 12 rib on the way things should be a little more acurate with the boost levels.

 

[matt texass]

Awesome. What did you make on 15#?

 

[andyman]

Also how high do you spin the engine 05stroker?

 

[05stroker]

Awesome. What did you make on 15#?

617 / 550 at 15 psi and 93 oct .

 

[05stroker]

Also how high do you spin the engine 05stroker?

I think it was 6600 but cant remember for sure . The sheets are in my build thread . To be honest with the stock intake the pulls usualy level off from 5800 up anyhow . ( the reason I have the JPC intake now) Even on my 700+ race tune the power is made by 5800 . That is why I am very excited about this new setup with the JPC intake and the bigger exhaust . I have had it to 7500 though . ( on the dyno, 7200 on the street )

 

[psfracer]

Either that or a high boost low timing setup for the street. That way I dont have to change anything but the tune .

That is exactly what I did when I street drove my mustang at 16psi with the whipple. I put alot of miles on it this way, and it drove fine. Total timing was 13 degrees, but it was safe. When I went to the track, I just added race fuel and the race tune, which had 23 degrees at WOT.

 

[don_w]

That is exactly what I did when I street drove my mustang at 16psi with the whipple. I put alot of miles on it this way, and it drove fine. Total timing was 13 degrees, but it was safe. When I went to the track, I just added race fuel and the race tune, which had 23 degrees at WOT.

I still don't trust the 91 octane gas... I keep mine at 15psi (or less) on the street. Can't use all that power anyway, so why have it. LOL

 

[psfracer]

Because its a pain in the ass to change pulleys all the time. Especially when you drive the car to the track, race, then drive home. I didn't want to deal with that every other week when I raced.

 

[05stroker]

That is exactly what I did when I street drove my mustang at 16psi with the whipple. I put alot of miles on it this way, and it drove fine. Total timing was 13 degrees, but it was safe. When I went to the track, I just added race fuel and the race tune, which had 23 degrees at WOT.

I wonder if the same will work at 22-24 psi ? I would assume so , just low timming and it should be good . The aits will be higher , but the low end tq will still be there by running the smaller pulley .

 

[don_w]

Because its a pain in the ass to change pulleys all the time. Especially when you drive the car to the track, race, then drive home. I didn't want to deal with that every other week when I raced.

Changing a pulley on a KB is easy.

 

[05stroker]

Because its a pain in the ass to change pulleys all the time. Especially when you drive the car to the track, race, then drive home. I didn't want to deal with that every other week when I raced.

True and with very low timing the big power is not there anyway , just some more low end from the smaller pulley .

 

[05stroker]

Changing a pulley on a KB is easy.

It is on a Procharger to , but if you dont have to on a car that has limited street dutys and can pick up a little more low end torque for the street with low timing on 93 oct then its nice and easy when all you have to do is change the tune .

 

[don_w]

It is on a Procharger to , but if you dont have to on a car that has limited street dutys and can pick up a little more low end torque for the street with low timing on 93 oct then its nice and easy when all you have to do is change the tune .

We don't have 93 here... just 91.

 

[05stroker]

We don't have 93 here... just 91.

That becouse you live in Wehateeveryonebecididesthetreesandaircalifornia !