Compression for my ls E85 motor
Compression for my ls E85 motor So I have a forged ls 370" with 317 heads now running 9.20@148. car made 798 to the wheels@19psi boost. looking to mph the car at about 155mph. Current static compression is 9.2:1 with the 70cc 317's. I am having my all pro heads reapired and they can make the cc of the combustion chamber from 62 to 70cc. This could result in static compression from 9.2 to 10:1. Im using E85. What is your input for compression. Here are some specs:
370 motor with -11cc wiseco pistons
Turbo is forced inductions s484 with t6 96mm wheel
cam is a tick 232/236 .625/.610 On a 115
powerglide with 3.25 rear end ratio
3400lbs with driver
Thanks for any input,
James
370 motor with -11cc wiseco pistons
Turbo is forced inductions s484 with t6 96mm wheel
cam is a tick 232/236 .625/.610 On a 115
powerglide with 3.25 rear end ratio
3400lbs with driver
Thanks for any input,
James
It'll love some more compression but I will say this when I built a 370 using the same pistons and that same turbo and cam from Martin he actually preferred the 9:1 compression to not create as much back pressure if I remember correctly.
E 85 is a sweet fuel and you should be just rite with 10 to 1 as always there's trade off, lest just say you should not have much turbo lag off the line with 9+ compression, with 10 to 1 you'll live harder and spool faster so speed will build quicker, and if you total advance timing suffers (I don't think it will) as the case with gas you can still add 99% methanol -OMG.
Just have in mind for all out racing 11 to 1 to 11.5 compression is used in similar cubes with twin turbos.
After milling heads de burr all sharp edges around the combustion chamber perimeter as well as spark plugs holes threads ends if sharp edges, will help run more timing if desire to add torq.
Just have in mind for all out racing 11 to 1 to 11.5 compression is used in similar cubes with twin turbos.
After milling heads de burr all sharp edges around the combustion chamber perimeter as well as spark plugs holes threads ends if sharp edges, will help run more timing if desire to add torq.
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How hard are you pushing the turbo? I run the stock lq4 ~9.4;1 compression ratio with E85. Have thought about more CR but afraid of tearing up parts.
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10:1 should be fine. The AllPro are going to flow much better and overall PSI will/should drop with CFM staying the same. Less PSI means less heat.
I wish SO bad I had E85 here.
I wish SO bad I had E85 here.
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I also looked into going with more compression and according to most higher compression will give you more power before boost but also narrow your tuning window. In a street car when you aren't into boost all the time it helps get the car going before boost really kicks in.
I ran those times with the PT88 then I switched the exhaust flange to a t6 and put on the s484. Went the same exact time and mph with the same boost. I have come the the conclusion that I have a cam with alot of overlap which is causing back pressure issues, and I was floating the valves. It would get worse after 17psi and after 21 to 22 it would make no performance difference. The data log at 17 to 18psi showed a nice rise in RPM off the transbrake with an 800rpm shift drop then a nice rise to the end of the quarter. Every additional pound of boost after that and the rpm of the data log would rise off the tranbrake then flat line.
I just spoke to Martin and he recommended for my set up with the cam he spec'ed 10:1 as optimum use of E85
I have been 9.20@148 @ 19 psi. I ran it all the way up to 24psi but it did not go any faster.... I am will not take it any further than my cage cert which is 8:50. Anything with an 8 second time will do...I am hoping with the stiffer springs and less overlap cam and better flowing heads I will be able to run an 8 second pass with 22-23 lbs.
The ALL pro heads I have are currently @ 70cc but my machinist said he can weld them up and make them anything I want from 62cc to 70cc I think I am going to try the 10:1
I ran those times with the PT88 then I switched the exhaust flange to a t6 and put on the s484. Went the same exact time and mph with the same boost. I have come the the conclusion that I have a cam with alot of overlap which is causing back pressure issues, and I was floating the valves. It would get worse after 17psi and after 21 to 22 it would make no performance difference. The data log at 17 to 18psi showed a nice rise in RPM off the transbrake with an 800rpm shift drop then a nice rise to the end of the quarter. Every additional pound of boost after that and the rpm of the data log would rise off the tranbrake then flat line.
Thanks, It is really a learning adventure. It's one I enjoy though. The old cam is 235/247 .647/.657 114 Lobe center and 114 intake C/L. The new cam is much milder with lift and duration, and spring pressure was 140 closed/411 open and new milder cam spring pressure is 170 closed 475 open. I should add that I am running shaft rockers also.
I do have a build page for this it is here: http://www.turbobuick.com/forums/thr...evy-ii.270436/
I originally had a turbo v6 in it that is why it is on that site but it goes all the way up to the installation of the ls v8
I do have a build page for this it is here: http://www.turbobuick.com/forums/thr...evy-ii.270436/
I originally had a turbo v6 in it that is why it is on that site but it goes all the way up to the installation of the ls v8
Last edited by turbo6man; Oct 8, 2014 at 07:16 PM. Reason: link error
Yeah I must have been mistaken. I just remember you had a reason for preferring the compression of my motor at 9:1 with the stage 2 cam you spec'd me and the s484. I thought it was a back pressure issue but it must have been something else. My bad Martin
No need to apologize sir! If you have anymore questions or concerns regarding your build feel free to call or email me at anytime.
Thanks Chris and Martin Well my All Pro heads ended up that they were going to cost as much as it would be to get a new set of TFS 13.5 degree 16 bolt heads. So Chris Frank and I went back to scratch and he recommended the optimum cnc/valve size and combustion chamber. It turns out he has a bunch of different cnc programs for those heads depending on set up. He was very nice to speak to and just like Martin at tick who helped me, took the time to explain everything.
