increasing compression
#1
increasing compression
I have decided to increase my static comp. from the usual 8.8:1 weiscos to roughly 9.5:1..yes the weiscos that FM sell are actually lower then advertised"no big deal"
I have done some research on this matter,not inc already haveing been around alot of 10:1 -11:1 turbo motors but these have all been on race fuel "c16"
As some of you may know I have been using 93oct with 50/50 water/meth, and have had very strong and consistant results for the last 3 years.
I normally dont share to much R&D during my build but thought this may be interesting to some of you..
I am doing this not so much for max power, but rather trying to get more off boost power and better spool response
I have witnessed some very strong results with comp. increase on hondas and the evo 8's which btw is very similar cumbustion chambers size, piston size etc
I also have seen good #s from ls3 and ls7 with very high comp. and they have run over 10psi with no problems, to name a few more.
Your opinions and facts would be appreciated on this matter as I will post final dyno#s and other data logs on this site..
I have done some research on this matter,not inc already haveing been around alot of 10:1 -11:1 turbo motors but these have all been on race fuel "c16"
As some of you may know I have been using 93oct with 50/50 water/meth, and have had very strong and consistant results for the last 3 years.
I normally dont share to much R&D during my build but thought this may be interesting to some of you..
I am doing this not so much for max power, but rather trying to get more off boost power and better spool response
I have witnessed some very strong results with comp. increase on hondas and the evo 8's which btw is very similar cumbustion chambers size, piston size etc
I also have seen good #s from ls3 and ls7 with very high comp. and they have run over 10psi with no problems, to name a few more.
Your opinions and facts would be appreciated on this matter as I will post final dyno#s and other data logs on this site..
#2
We had a huge discussion on this a while back. Huge debate of what's really happening when changing compresion ratios. What leads you to believe that increasing compression will increase spool? If you're still gonna run a bunch of boost like before I wouldn't get in too big of a hurry to get the compression up.
Nitrous helps spool and off boost power too.
Nitrous helps spool and off boost power too.
#3
Recently an Evo specific tune/build shop underwent some testing with compression ranging from low 8s to low 10s and they found major spool increase..A couple of other well known tuner/builders chimed in and said they had the same results..
Typically they saw a 300rpm earlier spool from the factory 8.8 to an extra 1 point in compression with no other changes and an added benefit of 20whp across the board.
I spoke to someone that worked on the earlier eclipse's with Shepard racing and the more comp. they ran the faster the car went in every aspect of the track.
So I did enough homework to convince myself to undergo this on our own miata..
Typically they saw a 300rpm earlier spool from the factory 8.8 to an extra 1 point in compression with no other changes and an added benefit of 20whp across the board.
I spoke to someone that worked on the earlier eclipse's with Shepard racing and the more comp. they ran the faster the car went in every aspect of the track.
So I did enough homework to convince myself to undergo this on our own miata..
#4
Hmm, well, I've seen cars drop compression and gain spool too. Anyways, sounds like you've already made up your mind. How much boost are you planning to run at this new higher compression? If you have a tuner that can dial in a high comp boosted engine it should be fine. But as you know it will be less forgiving.
I think it goes without saying that for the average, turbo DIY'er, a low com, high boost motor is preferred as it's more forgiving to a less than perfect tune.
I think it goes without saying that for the average, turbo DIY'er, a low com, high boost motor is preferred as it's more forgiving to a less than perfect tune.
#10
Ok, I'm still a newb here, but as far as I can tell, the compromises you make to a decent turbo set up in order to run higher compression outweigh the slight benefit of quicker spool. The "20hp across the board" is secondary, as on a FI car there are plenty of quicker ways to pick up that 20hp, like getting a larger trim snail and sacrificing 300rpm of spool for example.
To me, if spool is so important, it's much easier to build a regular setup on a low compression motor with the initial turbocharger matching your needs. But then again, I've turboed 0 EVOs.
To me, if spool is so important, it's much easier to build a regular setup on a low compression motor with the initial turbocharger matching your needs. But then again, I've turboed 0 EVOs.
#12
Why bother going to that expense?
MX-5 Miata Forum - Building high compression pistons
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MX-5 Miata Forum - Building high compression pistons
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#17
Ok, I'm still a newb here, but as far as I can tell, the compromises you make to a decent turbo set up in order to run higher compression outweigh the slight benefit of quicker spool. The "20hp across the board" is secondary, as on a FI car there are plenty of quicker ways to pick up that 20hp, like getting a larger trim snail and sacrificing 300rpm of spool for example.
To me, if spool is so important, it's much easier to build a regular setup on a low compression motor with the initial turbocharger matching your needs. But then again, I've turboed 0 EVOs.
To me, if spool is so important, it's much easier to build a regular setup on a low compression motor with the initial turbocharger matching your needs. But then again, I've turboed 0 EVOs.
The next logical turbo up would have been an hta3582r but the loss in spool and transient response was not worth the increase in peak power.