Jump to content
SAU Community

Recommended Posts

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?

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

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.

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...

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. :)

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 by 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.

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

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.

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?

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 by 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.

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 by DennisRB30

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?

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.

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 :D 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.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Cheers. Skyline is back on the menu, can’t get rid of it. It’s like a child you don’t want, or herpes 
    • I got back to Japan in January and was keen to get back on track as quickly as possible. Europe is god-awful for track accessibility (by comparison), so I picked up a first-gen GT86 in December just to have something I could jump into right away. The Skyline came over in a container this time and landed in early January. It was a bit battered after Europe, though—I refused to do anything beyond essential upkeep while it was over there. The clutch master cylinder gave out, and so did the power steering. I didn’t even bother changing the oil; it was the same stuff that went in just before I left Japan the first time. Naughty. Power steering parts would’ve cost double with shipping and taxes, so knowing I’d be heading back to Japan, I just postponed it and powered through the arm workout. It took a solid three months to get the car back on the road. Registration was a nightmare this time around. There were a bunch of BS fees to navigate, and sourcing parts was a headache. I needed stock seats for shaken, mistakenly blew 34k JPY on some ENR34 seats—which, of course, didn’t fit—then ended up having the car’s technical sheet amended to register it as a two-seater with the Brides. Then there’s the GT86. Amazing car. Does everything I want it to do. Parts are cheap, easy to find, and I don’t care what anyone says—it’s super rewarding to drive. I’ve done a few basic mods: diff ratio, coilovers, discs, pads, seat, etc. It already had a new exhaust manifold and the 180kph limiter removed, so I assume it’s running some kind of map. I’ve just been thrashing it at the track non-stop—mostly Fuji Speedway now, since I need something with higher speed after all that autobahn time. The wheels on the R34 always pissed me off—too big, and it was a nightmare getting tires to fit properly under the arches. So I threw in the towel and bought something that fits better. Looks way cleaner too (at least to me)—less hotboy, less attention-seeking. Still an R34, though. Now for future plans. There are a few things still outstanding with the car. First up, the rear subframe needs an overhaul—that’s priority one. Next, I need to figure out an engine rebuild plan. No timeline yet, but I want to keep it economical—not cutting corners, just not throwing tens of thousands at a mechanic I can barely communicate with. And finally, paint. Plus a bit of tidying up here and there.  
    • Nope, needed to clearance under the bar a little with a heat gun, a 1/2" extension as the "clearancer", and big hammer, I was aware of this from the onset, they fit a 2.0 with this intake no problems, but, the 2.5 is around 15mm taller than a 2.0, so "clearancing" was required  It "just" touched when test fitting, now, I have about 10mm of clearance  You cannot see where it was done, and so far, there's no contact when giving it the beans Happy days
    • It's been a while since I've updated this thread. The last year (and some) has been very hectic. In the second-half of 2024 I took the R34 on a trip through Germany, Italy, France and Switzerland - it was f*cking great. I got a little annoyed with the attention the car was getting around Europe and really didn't drive it that much. I could barely work on the car since I was living in an inner-city apartment (with underground parking). During the trip, the car lost power steering in France - split hose - and I ended up driving around 4,000kms with no power steering.  There were a few Nurburgring trips here and there, but in total the R34 amassed just shy of 7,000kms on European roads. Long story short, I broke up with the reason I was transferred to Europe for and requested to be moved back to Japan. The E90, loved it. It was a sunk cost of around EUR 10,000 and I sold it to a friend for EUR 1,500 just to get rid of it quickly. Trust me, moving countries f*cking sucks and I could not be bothered to be as methodical as I was the first time around.
×
×
  • Create New...