Radical Changes In Fuel Pressure With Malpassi.

[DennisRB30]

So I set my malpassi to 50psi base (referenced to atmospheric) Then had a look a week later and its at 30psi. My car was going VERY hard at that fuel pressure with wheelspin through first and second with 0.7bar. So I put it back to 50psi as I think it was at 50 when we tuned it. (I say THINK because I set it a few days before we tuned it and it may well have went down before we tuned it).

After I put it back to 50 I went for a drive and the car ran like crap and was misfiring. So I checked it again and it was at 75psi base! I put it back to 50 again and it seems to be staying there now.

WTF is going on?

[R31Nismoid]

I've heard the Malpassi have been known to have problems such as what you've described where by the pressure is all over the place.

Not sure if its a product or installation thing... but then... its not hard to install one so i think i'd go with product

[TurboX]

I would be checking the reference air lines as it only can work with what it sees from your manifold unless it has a diaphram problem or similar.

Aside, I thought the base ref was 43 PSI?

Though I seem to have killed four gauges till I figured the one way valve that was removed from on the in tank Bosch 044 may be needed in the line to stabilise the gauge from high speed fuel pump pulsations.

Have not fitted new gauge yet to see if putting in line has solved problem.

[dangerous_daveo]

50psi!!! Mines on 30psi at 800rpm idle. I also have the standard dr drift rb20det chip and its a flat 12afr, and I do mean flat. So Im guessing try going back down a few psi first.

Where the problem might be is in what model malpassi you have and where its located.

#1 if its ratio is wrong its going to pump in way too much fuel. I had a black top one on mine a while ago and had the same problems you have. I then replaced it with a silver top and all was good.

#2, if its near excessive heat this apparently CAN have an affect on its performance. That said mines bolted to a bracket on the side of my plenum and is spot on perfect in winter and after sitting in 1hour of summer traffic...

[Beer Baron]

I've said it before and I'll say it again. I wouldn't put a malpassi regulator even near my car. They should call them de-regulators. cheap pieces of crap. through it in the bin before you lunch your motor.

[DennisRB30]

Its a black top 1.7:1.

It is installed on my strut tower away from heat and vibration. I can't see how my installation could be causing the probs. Its fairly straight forward to install.

I also have a intank 044 with the valve removed. I have noticed my gauge reads 5 psi with the pump off, which is wrong as it should read zero with no valve in the system.

I always set the base pressure in reference to atmospheric pressure, IE with the vacuum line off (so the lines are not a factor, plus they are all OK anyway). So 50psi is only a bit above standard. At idle its 25psi.

Edited March 1, 2007 by DennisRB30

[DennisRB30]

I've said it before and I'll say it again. I wouldn't put a malpassi regulator even near my car. They should call them de-regulators. cheap pieces of crap. through it in the bin before you lunch your motor.

That is what I have been hearing. What actual experience do you have with them? I would like to here some first hand info as opposed to regurgitated hearsay.

[Tex Willer]

I've said it before and I'll say it again. I wouldn't put a malpassi regulator even near my car. They should call them de-regulators. cheap pieces of crap. through it in the bin before you lunch your motor.

Agreed. 1 of 2 fails. IMO

[DennisRB30]

Agreed. 1 of 2 fails. IMO

What do you mean exactly by "fails". Failure can be relative.

[Guilt-Toy]

I've said it before and I'll say it again. I wouldn't put a malpassi regulator even near my car. They should call them de-regulators. cheap pieces of crap. through it in the bin before you lunch your motor.

AGREED.. they hardly ever work properly. get a sard for the min. many people have lost engines because of malpassi's dont be another victim. replace it asap. dont hit boost untill thats done.

[DennisRB30]

AGREED.. they hardly ever work properly. get a sard for the min. many people have lost engines because of malpassi's dont be another victim. replace it asap. dont hit boost untill thats done.

f**k this. I have been hearing this all to often. It scared the shit out of me when I saw it was running 25psi less than what I set it to.

Will a this Sard be OK? http://cgi.ebay.com.au/SARD-Fuel-Pressure-...1QQcmdZViewItem

I have heard from someone that they are not the all that good either. But my mate has one on his Aristo with a 044 fuel pump and it seems to be OK. It says its rated for max 450 HP? I will be running a lot more than that. Does anyone else use a Sard with 500+ RWHP?

[DennisRB30]

I finally figured the Sard FPR's out.

http://www.upgrademotoring.com/performance/sard_reg.htm

The Ebay ones appear to be the 450hp ones. The bigger one costs a lot more. So what would happen with a 450 one? My guess is that if you use more than 450hp worth of fuel the pressure starts to drop since it can't handle such a large variation in flow.

My mate with the Aristo with the Sard changed from a stock fuel pump to a 044 and base pressure shot up by like 20psi. Some people might say, well DUH there is more fuel flow. But to me that is a sign off poor regulation with varying fuel flow. What happens when the engine is using most of the fuel flow from the pump at high load? My guess is the pressure will drop. If pressure goes up by 20psi with more X amount fuel flow, its going to go down by like 20psi when the engine uses X amount of fuel flow up. Does that make sense?

His sard does seem to be stable though. Its always the same when you check it unlike the malshitty.

Edited March 1, 2007 by DennisRB30

[R31Nismoid]

The sard wouldnt "increase" unless it was set to do this.

Just changing pump wont increase the fuel pressure if the pump is on good order

UNLESS the pump that was in there was dying and wasnt keeping up the pressure, and hence the reg was bumped to compensate without realising.

[DennisRB30]

The sard wouldnt "increase" unless it was set to do this.

Just changing pump wont increase the fuel pressure if the pump is on good order

UNLESS the pump that was in there was dying and wasnt keeping up the pressure, and hence the reg was bumped to compensate without realising.

There was nothing wrong with the old fuel pump. We were running 0.9 bar with a T04Z on a 2JZ with 11.8 AFR's at 50psi base pressure, you can't ask for more out of a stock pump! But we changed it to an 044 so we could wind the boost up to be safe.

So I would say that changing the pump DOES increase fuel pressure if the FPR is being overwhelmed with fuel flow. That is my theory. It leads me to believe that the 450hp Sard is too small to regulate pressure effectively with a 044 pump.

Edited March 1, 2007 by DennisRB30

[R31Nismoid]

50psi base once, 50psi base another time... you guys all gambling with stock injectors?

A FPR that is the same ratio as the one you replaced, will not alter fuel pressure

[Guilt-Toy]

I turned my rb25 into macaroni and cheese with a malpassi. I now run a sard - might be upgrading it because im past the 450hp mark so make a offer

f**k this. I have been hearing this all to often. It scared the shit out of me when I saw it was running 25psi less than what I set it to.

Will a this Sard be OK? http://cgi.ebay.com.au/SARD-Fuel-Pressure-...1QQcmdZViewItem

I have heard from someone that they are not the all that good either. But my mate has one on his Aristo with a 044 fuel pump and it seems to be OK. It says its rated for max 450 HP? I will be running a lot more than that. Does anyone else use a Sard with 500+ RWHP?

[Abo Bob]

I think you need to look back to the start here.

You set it to 50 psi, then you checked it and it was 30 psi, so you increased it to 50 psi, then you checked it and it was 75 psi.

It seems to me that the malpassi didn't change it's pressure at all. Either you stuffed up the reading of the pressure when you thought it was 30 psi or your gauge read it wrong.

It looks like you got an incorrect reading, increased the pressure, got a correct reading, reduced the pressure back to where it should have been.

That said I also am not a Malpassi fan. I had one and had erratic fuel pressure so I ditched it.

[CEF11E]

I had one of those sard FPR's on my last car and the pressure was 100% stable.

[DennisRB30]

50psi base once, 50psi base another time... you guys all gambling with stock injectors?

Yeah stock ATM, but to be upgraded very soon. In fact I am doing mine Today BTW its only 7psi more than standard.

A FPR that is the same ratio as the one you replaced, will not alter fuel pressure

In relevance to the increase in fuel pressure on the Aristo, this statement is wrong on so many levels.

Firstly, when the prob occurred we didn't change the reg, we changed the PUMP.

Secondly, all pressure references we made are to atmospheric. So if its rising rate it wouldn't matter.

Thirdly the Sard reg is a 1:1 reg anyway and it DID alter fuel pressure with the bigger pump.

Fourthly, or course if you change the reg the fuel pressure will change, its not like they automatically come set to exactly what ever fuel pressure you were running previously!

As you say the pressure shouldn't change. But it if does something is not right! Seems pretty obvious that the Sard reg is too small and can't flow enough fuel to keep pressure down with a 044 pump. This shouldn't be surprising since the Sard FPR is rated at like 250 horsepower less than the 044 pump! Thats probably why they make the bigger one.

Guilt toy, what happend with the Malpassi, are you sure it was at fault? No thanks for the offer on the Sard. It will be too small since I already have over 450hp.

Bob, I didn't stuff the readings up. Its pretty hard to stuff it up.