Engine 8.5:1 compared to 9.0:1
http://www.youtube.com/watch?v=skly2gsdbyU
We've been running high compression for a LONG time. We've run as high as 11.5:1 on straight pump gas at up to 34 psi of boost, no issues and great results. Video speaks for itself. Making power on pump gas, high compression blah blah, is nothing new around here.
The topic question, 8.5 compared to 9 is such a small increase/decrease I wouldn't put any thought into either.
Most of the engines we are building now are 10:1, very few exceptions.
We've been running high compression for a LONG time. We've run as high as 11.5:1 on straight pump gas at up to 34 psi of boost, no issues and great results. Video speaks for itself. Making power on pump gas, high compression blah blah, is nothing new around here.
The topic question, 8.5 compared to 9 is such a small increase/decrease I wouldn't put any thought into either.
Most of the engines we are building now are 10:1, very few exceptions.
Thanks for your input. Would you recommend staying on 10:1 for e85 or would you up it to 11:1 ?
We have found that the harder you push, whether its boost, compression, or timing on pumpgas, the closer the car is to problems. Dave has shown it many times, as have we, that for a given compression ratio the differences are really small. Application has a lot to do with it too I think. What you can get away with on the dragstrip doesnt translate to the road course or in a highway pull. High compression in a rally motor might work really well in endurance racing because squeezing the heck out of nothing is only slightly higher nothing. Do the same thing in a car like the Sierra Sierra car and it doesnt work as well.
Jeff's 1G (the Big Auto) has ran everything from 8.5:1 pistons all the way to 11:1s in the search for more power and it really hasnt made a difference in what the car does. Different pistons, 45psi, the same timing, the same cams, still the same results.
Dave, I presume that when you ran the 11.5:1 compression on 34psi it was at the edge of diminishing returns?
I have found on our 92 that I can run 30-32psi but not always make anymore power than running 29psi if I cant run more timing at the same time. Improve the VE and it definitely changes what I can do with timing and then the power will go up. I made 565whp on my car at 28-31psi on the dyno going up on the boost a pound at time but no more timing. Nothing changed. Then I lowered the boost back down to 29psi and added 1* and picked up 10whp. This was on my stock 2.0L and it was funny I couldnt run more boost on the dyno but the car would run 32psi on the street and track just fine.
cliffs- 9:1 seems to work best, run more boost.
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hmmm so what i read..... 10:1 everyone likes it seems like. but there isnt too much of a differance between 8:5 - 10:1..
10:1 on E85 is great from what i read but what about 10:1 on pump and meth?
10:1 on E85 is great from what i read but what about 10:1 on pump and meth?
Stroking the engine by far makes the largest difference in off boost feel, nothing else compares to the gain from stroking.
There is also more to the combination and raising the compression. The is MAJOR differences in the timing you will be able to run from one piston to another with the same compression, dome shape is very important. We've changed our piston design probably 20 times over the years and the majority of those have been in the last few years. There IS a difference.
There is also more to the combination and raising the compression. The is MAJOR differences in the timing you will be able to run from one piston to another with the same compression, dome shape is very important. We've changed our piston design probably 20 times over the years and the majority of those have been in the last few years. There IS a difference.
Stroking the engine by far makes the largest difference in off boost feel, nothing else compares to the gain from stroking.
There is also more to the combination and raising the compression. The is MAJOR differences in the timing you will be able to run from one piston to another with the same compression, dome shape is very important. We've changed our piston design probably 20 times over the years and the majority of those have been in the last few years. There IS a difference.
There is also more to the combination and raising the compression. The is MAJOR differences in the timing you will be able to run from one piston to another with the same compression, dome shape is very important. We've changed our piston design probably 20 times over the years and the majority of those have been in the last few years. There IS a difference.
....so assuming all else remains the same, mpg would be worse with the 2.3L vs 2.0L, but likely not noticeable...
I got 24mpg in the 2.0l, 24mpg in the 2.2, and 24mpg with the 2.4. The bigger the motor the less it works (as evidenced by the vacuum reading) so the mileage doesnt seem to suffer. This was all with the same or similar cams, intake manifold, injectors, and turbo kit.
I got 24mpg in the 2.0l, 24mpg in the 2.2, and 24mpg with the 2.4. The bigger the motor the less it works (as evidenced by the vacuum reading) so the mileage doesnt seem to suffer. This was all with the same or similar cams, intake manifold, injectors, and turbo kit.
Have you had any experiences with compression ratio increase and MPG's effects?
Since off boost power is increased the engine isn't working as hard. The 10:1 2.2 actually got 25mpg on one or two occasions when driving pure highway. The 2.4 seems to average 23.8 or so on most trips. On smaller cams I have gotten better mileage so some of it is debatable but the 2.0-2.4 seem to be in the same neighborhood for the most part when it comes to mileage. E85 mileage is the same deal.