Fuel Pressure Regulator for VVTi

[Jesus-Ninja]

My 1998 engine has (had) the in tank regulator with no return to tank from the engine. It's all going into an MX5 (Miata for the Yanks), but has a walbro and uses a return to tank. What is the recommendation for FPR, without using the stuff from the original LS400 tank?

I have an adjustable FPR lying around (one of these: http://www.demon-tweeks.co.uk/perfo...ompetition-adjustable-fuel-pressure-regulator) and was planning to run the pump into this, take a feed from the high pressure side to the fuel rail, and use the return to tank.

What is the base pressure I need? Do I need vacuum assist, or just a fixed pressure?

Thanks

 

[gloverman]

You have the system right. No vaccuum assist , around 60psi constant pressure works well.

 

[Jesus-Ninja]

Splendid. Pics to follow

 

[Jesus-Ninja]

I seem to overfueling something chronic (see video below). Everything in terms of fueling and engine management etc is stock, so am not sure what the issue is. Winding back the fuel pressure causes idle to drop off, so 60PSI must be about right.

http://youtu.be/XwCiWQ66uq4

 

[Spinnetti]

Why 60psi? aren't all Toyota EFI (and most others) like 42PSI?

 

[gloverman]

Returnless system by many manufactures run around the 60psi.

Have you checked the live data to see if anything is noticable? Also any codes?

 

[Jesus-Ninja]

Panic over. I realised that the "over fueling" only occurred after I had fitted the rear half of the exhaust system. The front half is all new (made by me), from the y piece back is a second hand 2.5" system from a turboed MX5. Took the rear half off, and no soot.

Diagnosis is a second hand system from a rich car that's been bounced around by the postman on it's way here. A few laps should clear it

 

[George_R]

60 psi is way too much
1uz vvti (as well as 3UZ and other newer toyota engines) uses 3.3 bar +- something, that's listed in the FSM
that's about 48 psi only

60 psi is 25% more than the normal pressure so engine management system is likely to have problems with fuel trims (which are normally +-20% only)

 

[gloverman]

When I first started doing VVti engines we put a few onto the dyno and monitored the mixture , trim and power. By increasing the pressure we saw increased power without big changes in the fuel trims. With several fuel economy runs we found that over 60 we lost fuel economy. The end result was setting between 55 and 60.

Remember the relationship between pressure and flow. Increasing the pressure by 25% results in a much smaller increase in fuel flow.

 

[George_R]

gloverman thanks heaps for the important info
I've recently come across fuel filter for modern (last gen) skoda, vw, audi and the like (Kolbenschmidt 50 013 971 , has a lot of direct replacements). It has 4bar regulator built in (which is 58 psi perfectly, has lots of direct replacements and costs just about $20). Will definitely have a try with one of these as it greatly reduces the number of connections in fuel system

p/s can you recall what sort of hp/tq gain should one expect when raising the pressure from stock 48psi to the value of 55-60 that you suggest?