BC GTA

Does anyone have any hard evidence that increasing the stock fuel pressure 5 to 6 lbs/hr will really result in horsepower increase? I have a 1989 Trans Am GTA with a new TPI 5.0 liter long block, with a: comp cam, headman headers, improved exhaust system with no catalytic converters, K&N air filter, Bosch mass airflow sensor with the screens removed, MSD distributor, coil and wires. I performed a throttle body coolant bypass and decided not to get a bigger throttle body with advise from this web site. I recently reviewed all the posts and articles from this web page regarding porting the plenum and runners. I phoned two specialty auto machine shops in my hometown regarding porting/polishing the stock heads who advised it was not worth it. I am going to attempt porting the plenum and runners myself and stop there with the intake system. I reviewed all the posts and articles regarding adjustable fuel pressure regulator, as this would be the time to consider it. I would get the Holley fuel pressure regulator due to their good name as well as other regulators' adjustable screw had to be modified because the screw is too long. However, I have seen very little information that suggests increasing the fuel pressure, with such a small block set up, will actually increase horsepower. In fact one of the articles indicates this. Some people have suggested they would only increase the pressure when they race their car at their local track/drag strip. Almost all my driving would be urban with a few long trips on the freeway.

PHAT89TA

well i recently put the holley afpr on my tpi and i definatly felt a difference in performance. The car feels more responsive and have a definate increase on top end. I haven't gotten the car dynoed yet so i don't have any evidence it is faster, but it does feel faster. since u have a comp cam, headers, and ported plenums; afpr will be the perfect with those combo

87350IROC

iTrader: (2)

Turn your stock unit into an adjustable one for around $1 or maybe $5 if you don't have a welder. Seriously it works, why pay $60+ for an aftermarket one? This way if you don't see a difference you are only out a few bucks. Mine works fine. Vader has a tech article on how to do it.

http://www.gmtips.com/3rd-degree/dox/tips/afpr/afpr.htm

He suggests brazing but i found welding works fine too.

greenfrogg

wish i could of seen this article 2 weeks ago i bought the crane 1 and all i can say is i am glad i bought the cheapest 1 . after seeing the final product ,mine came with a slug[little metal circle] instead of the ball,other wise same thing as modification . it would of saved me $70 buck's

BC GTA

I just received the June 2000 issue of Hot Rod magazine referenced on the TPI message board for tuning these engines. That article discusses fuel pressure for TPI engines and recommends increasing the fuel pressure with an adjustable fuel pressure regulator. Although, the article is unclear on how much pressure is correct or how to determine what pressure is right for your engine. Does anyone have any suggestions on the right pressure for a 5.0 liter engine with a cam installed, or more useful the procedure for determining what is the correct fuel pressure for a particular engine?

LB9GTA

iTrader: (1)

BC GTA, get yourself a scan tool.
Find out what are the readings off of the 02 sensor and adjust accordingly. 840-900 millivolts I believe.
Every motor if different but I have a '91 gta with 305tpi(cam, headers, ported plenum, afpr and msd wires) and the best fuel pressure is at about 48 lbs and the timing is at 13-14 degrees.

LB9GTA

BC GTA

Thanks for the information. I will invest in a scaner and learn how to use it.