I posted the follwing question in thread https://www.rx7club.com/rtek-forum-168/progress-report-925797/ directed @ ARGHX but the thread's originator seemed to have gotten bent out of shape by "stealing" his/her thread. Oh well, roockie mistake and I promise not be a thief anymore. So here it goes: What max boost I should run w/ the Rtek 1.8. 91 octane is it @ the pump. Engine: '87 TII. Mods: street port, 3mm apex, BNR Stage 3 equivalent, free flow exhaust, 3" tubing AFM to turbo inlet, Godspeed FMIC (Greddy clone), stock ignition. Compression is ~108 psi on all surfaces. Air temp in this area is a stable 70F year round and low humidity. Also what 1/4 mile speeds have you had and @ what boost? thx much

 

I want to get to the same set up.

 

I don't know what kind of timing the 1.8 actually runs (it's supposed to be a little more retarded than stock, I had an Rtek 1.7 which is similar) but my biggest concern would first be getting a wideband on the car to see where the AFR is at for a given boost level. Back in the day I've ran 12psi with the stock turbo and FMIC on just the stock ECU + FCD, but that was on 93 octane.

 

The answer is: No one can tell you.
I get people calling all the time with similar questions. The answer depends on so many variables that no one could tell you for sure. I know that that's what a lot of people are looking for, a definitive answer, but it's just not possible. And do you really want some random person on the internet guessing at those hundred different variables to give you a 'definitive" number?

Listen to arghx. Before you get anything, get a wideband. As far as I'm concerned, there's no excuse not to have one if you are modding and/or raising the boost. At that point you can see where you are as far as fuel delivery goes and make an educated decision as to how much boost you can run, or if you'll need more mods to support a higher boost level. With a street port, everything goes out the window and IMO a stock ECU (even a stage 1.x) is not well suited for ported motors without a way to find tune the fuel. Can it be done? Absolutely. But you need to keep tabs on your AFRs.

 

thx for your input. you had an FCD in place with the 1.7? Didn't the 1.7 eliminate the need for it?

 

The UEGO sensor is on the purchase list but one step at a time. However, my thought on the '87 fuel control is that it is a, maybe crude, MAF system. That is, regardless of the mods, and assuming all sensors are working properly, the proper amount of fuel will be delivered as long as the amount of MAF is within the limits of the AFM. 4x720 cc injectors should support ~350 HP assuming .85 DC and .65 BSFC. Having said that, 12 psi boost is where I should be based on the old HKS Stage 5 claimed HP. I'd still like to hear from those who have experiened the 1.8. Might have to edit the title and the wording of my inquiry.

 

Im running a 1.8 with 720's and I go lean at 13psi. I dont trust my wideband though as the LC-1 has been a pain for me to calibrate. Stock turbo/streetport/FMIC/3" exhaust and intake. I get like 13.1 afr @ 13psi in 3rd gear. 12.5 afr @ idle. The car pulls hard though and breaks tire in 1st.

 

thx for your feedback. Surprising to see you're leaning out w/ stock turbo @13 psi. Doesn't seem 4x720 can support my guesstimated ~350 HP @ the crank. I like what I see in your idle mixture.