Mild mods and an AFPR?
Thread Starter
Instructor
Joined: Dec 2013
Posts: 142
Likes: 0
From: Bothell WA
Mild mods and an AFPR?
'85 TPI.
My car had an AFPR, K&N and the open front airbox when I bought it, along with a tranny swap. I don't think there's any other mods. No rockers, stock throttlebody, runners, etc. Nothing ported. It was running at 45 PSI, but I had a really rich smelling exhaust. Normal?
Anywase, I needed to get a new throttlebody and I had a 58mm plenum sitting around so I bought a 58mm Holley throttlebody.
My question is, I feel like 45 PSI was WAY too much for what it was when I bought it. But how much PSI do you guys think I should be running now with the 58mm plenum and throttlebody? Still the stock runners. Those are going to Edelbrock Hi-Flows later.
My car had an AFPR, K&N and the open front airbox when I bought it, along with a tranny swap. I don't think there's any other mods. No rockers, stock throttlebody, runners, etc. Nothing ported. It was running at 45 PSI, but I had a really rich smelling exhaust. Normal?
Anywase, I needed to get a new throttlebody and I had a 58mm plenum sitting around so I bought a 58mm Holley throttlebody.
My question is, I feel like 45 PSI was WAY too much for what it was when I bought it. But how much PSI do you guys think I should be running now with the 58mm plenum and throttlebody? Still the stock runners. Those are going to Edelbrock Hi-Flows later.
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
A 58 mm TB is waaay too big for a stock, or close to stock engine, and will only create an off idle hesitation more so than any performance possibly gained. Stock pressure for the 17085050 fuelrail was 39 psi. Setting it to no more than 41 would be a maximum unless dropping to a smaller injector than the stock Bosch 280-150-223's at 23.5 lbs. Fuel pressure is always set without vacuum applied.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
Fuel pressure affects how much fuel the injectors squirt when they are pulsed by the ECM. The ECM will compensate for a change in pressure while in closed loop mode and the net gain is nothing.
That said, you should check the BLMs to make sure the ECM isn't "hitting the stops". The BLMs are limited and if the ECM hits a limit then it can't compensate any further and you will run rich or lean depending on which one you hit.
When the ECM is running in open loop mode (cold coolant or high throttle openings) then it is dependent on the injector constant and fueling tables. If the injector constant is not changed and/or the fueling tables are not adjusted to compensate for the modified injector flow rate then you can run rich.
That said, you should check the BLMs to make sure the ECM isn't "hitting the stops". The BLMs are limited and if the ECM hits a limit then it can't compensate any further and you will run rich or lean depending on which one you hit.
When the ECM is running in open loop mode (cold coolant or high throttle openings) then it is dependent on the injector constant and fueling tables. If the injector constant is not changed and/or the fueling tables are not adjusted to compensate for the modified injector flow rate then you can run rich.
