If i had a motor tuned with a 255 walbro fuel pump and then take it out and put it in a crx with a stock fuel pump, will tuning change? I forgot what my fuel pressure guage read when it had the 255 but now it reads 40-41 at idle, which is stock. I have this high idle problem and i'm thinking this can be the problem.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by UNKNOWN_MEMBER &raquo;</TD></TR><TR><TD CLASS="quote">If i had a motor tuned with a 255 walbro fuel pump and then take it out and put it in a crx with a stock fuel pump, will tuning change? I forgot what my fuel pressure guage read when it had the 255 but now it reads 40-41 at idle, which is stock. I have this high idle problem and i'm thinking this can be the problem.</TD></TR></TABLE>

If you use a high flow fuel pump with the stock regulator, you will have higher pressure at lower RPMs/loads due to the fact that the regulator cannot flow sufficient fuel at its 'set' pressure. The result is that pressure will increase until fuel flow through the regulator equals that delivered by the pump (which decreases with increasing pressure). So going back to stock for a 255lph pump will make the engine run leaner.

 

well if u put the stock pump back in the car, then u need to bump up the fuel pressure to what it was when u had the 255 pump. if u dont ur tune will be off = LEAN

 

Can anyone give me a rough estimate on how much a 255pump richens it up by? I'll just turn the fuel pressure up and use the stock fuel pump.

 

ttt

 

there has to be someone out there that knows how much more the pressure goes up by when putting a 255 pump

 

Were you using a fuel pressure regulator on your setup with the walbro 255 ?
There are two types of walbro 255 pumps, there is a high pressure pump & a normal 255lph.

You need to put your car back on the dyno using an adjustable fuel pressure regulator so you can set your fuel pressure where your tune wants it to be....

 

high pressure. well see thats the thing, i just need it to be a quick fix cause i'm going to the track on wednesday then take the motor out. I just put it at 46 at idle now. hopefully it'll work.