Who makes a decent vacuum adjustable regulator that fits in the stock TBI location?

 

On edit: I was going to point you to TDS for a factory GM regulator, but they don't appear to sell them anymore, just the stiffer spring.

You might see if your GM dealer can get you a stock vafpr that was used on the 454 trucks.

With that said, it's a real bear, if not impossible to tune around with a stock ECM. Rbob's EBL system has a table just for vafpr and takes all the guess work out of it and properly scales the injector size for each step in vaccume. On a stock ecm you can crutch the VE tables to get the fuel right, but there is no good way to crutch the pump shot so you can't really get a pump shot that is repeatable as the injector size is moving all over the place.

 

What do you mean when you say the injector size is moving all over the place ? Also what year model & platform do you speak of for the adjustable regulator?

 

The adjustable regulator came on the Marine TBI engines.

 

When the vaccume changes the fuel pressure changes, the problem is that the ECM doesn't know that the fuel pressure is changing. So it's like your injectors are constantly changing sizes.

The trick is to just tune the VE curve and not really worry that it looks all screwy as you are just tuning around the changing fuel pressure.

The part that you can't tune around is the pump shot as there is no way to tune it for the changing fuel pressure.

 

Thought that was what you meant BMmonte. If I were any better at math I would try to log the pressure increase/vacuum decrease vs. TPS timeframe, apply that to my inj output calc,and apply that to the AE airflow calc, but I usually get lost about halfway through on such things!

 

GM #17113186 - GM Adjustable Fuel Pressure Regulator. This is the one I purchased awhile back, but I think it's been discontinued. I've never used it so I can't tell you how it works though.

 

You can still get it through SDP.

 

i think the P4 PCM has a table for this. something about injector constant vs MAP. or maybe im way off here.

 

Found the part at SDP but no picture. Is it both vacuum regulated and manually adjustable?

 

Yes it is. I'll try to remember to pull it out and take a pic tonight.