shm21284

I'm planning on building a 12a turbo. I'm going to dowel pin it, use hardened stationary gears, give it a monster street port, and use otherwise stock parts. Yes, the apex seals and rotors (including compression of 9.4:1) will be stock.
I plan on using a t 04 turbo, front mount intercooler, and a holley 650 carburetor.
My question is, what do you all think about the stock compression rotors, because I have heard lots of different things such as detonation and less turbo lag (the higher the compression the rotors are, the quicker the turbo spools up). I personally know a guy who is using a TII turbo on his stock 12a engine and pushing 12 psi through it, non intercooled, and is not detonating.
So how will my stock compression rotors affect a t 04 running up to 15psi, intercooled (it's a larger volume of air, though, so more stress).
Let me know

hiboost7

well you are going to do the same setup i have on my 12a, except im not pinned. but the car should handl boost very well when pinned. i know a guy with a 12a turbo, monster street port, COMPLETELY stock internals running up to 28psi. crazy i know but im running 10 psi and thats plenty for me for a daily driver, 12psi to race....i wouldnt take the chance without being pinned, but since you are then got for it

shm21284

sweet

fitzwarryne

It should hold together but will test your seals. For a daily driver 8psi then perhaps 12psi for the occasional seious stuff. Remember Mazda kept stock down to 6psi for reliable performance even with low compression rotors.

Anymore can be expensive as the pins are only one side of the stress. But as you are rebuilding, the internals will be in good shape giving you more margin for heroics. Make certain your carb jetting is right.

web777

High compression rotors are fine. Just make sure you have plenty of fuel and your timing is right.

coldy13

Yep, my engine can take 16psi, non intercooled, on bone stock internals with 137k miles on them. I usually keep it down between 8 and 12 on the street.

fitzwarryne

It is simple to compare the difference between 12A/13B and 12AT/13BT [low compression] engines

Compression ratio x boost pressure ratio = effective compression ratio [ECR].

A higher CR and lower psi will give you the same ECR, as the opposite approach, and thus approximately the same maximum hp. However, the shape of the power curve will be different. The impact of the higher CR will be there throughout the entire rev range. In contrast the impact of the higher boost approach is only at higher revs when the turbo is effective.

Thus, the level of psi successfully used on a 12AT/13BT would be far too much for a 12A motor.