Stuttering at Spa?

[The Gorilla]

Hi,

If an engine requires 5 Bar fuel pressure at 200 GPH
then revs do not enter into it.

Going faster or slower does not alter the
delivery of fuel made by the pump, whereas
the engine may burn more or less fuel, if
its delivered at 5 Bar, there will always be
enough fuel.

There are no problems on long straights at WOT
pulling 7500/8000 rpm.

The only issue is when the pump is starved of fuel
and can not make the 5 Bar required, due to the
factor of G forces on longer radius bends washing
fuel away for prolonged periods from the pick up.

This has nothing to do with the pump.

Regards,

Thje Gorilla.

[cantfind1]

Hi,

If an engine requires 5 Bar fuel pressure at 200 GPH
then revs do not enter into it.

Going faster or slower does not alter the
delivery of fuel made by the pump, whereas
the engine may burn more or less fuel, if
its delivered at 5 Bar, there will always be
enough fuel.

There are no problems on long straights at WOT
pulling 7500/8000 rpm.

The only issue is when the pump is starved of fuel
and can not make the 5 Bar required, due to the
factor of G forces on longer radius bends washing
fuel away for prolonged periods from the pick up.

This has nothing to do with the pump.

Regards,

Thje Gorilla.

Yes people do have problems on long straights pulling 7000-8000 rpm and no sometimes the oem fuel pumps are not producing enough flow to give the required 5 bar. But you do not need 5 bar of pressure at low rpm!! Have you ever driven your car with a pressure gauge attached to see what happens??

5 bar is not required by the engine at low rpm the requirement for fuel to the engine increases with rpm therefore you have less flow back to the tank, this in turn affects the siphon system and makes it less efficient in cornering.

I am not going to argue the point anymore with you as it is tiresome Gorilla.

[The Gorilla]

Hi,

Cantfind1 - your correct that it is tiresome.

There is no flow back from the rail on a s54.

Regards,

The Gorilla.

[azrael]

I am not going to argue the point anymore with you as it is tiresome Gorilla.

I thought it was a discussion, no need to argue here :thumbs:

[glendog74]

Tiresome

:hahaha:

[shimmy]

I love all our technical discussions ESP when NZ_M3 and The Gorilla are involved.

Trouble is I am not clever enough to understand who is right everytime :bigcry:

[cantfind1]

Hi,

Cantfind1 - your correct that it is tiresome.

There is no flow back from the rail on a s54.

Regards,

The Gorilla.

BMW seems to think otherwise.
Check pipe number 3 in the diagram.

http://www.realoem.com/bmw/showparts.do?model=BL92&mospid=47621&btnr=16_0484&hg=16&fg=15

[_Nathan_]

That doesn't come back from the rail though which was the point being made - go and look at the rail on your car, it just stops at the front of the engine.

http://www.realoem.com/bmw/showparts.do?model=BL96&mospid=50641&btnr=13_0909&hg=13&fg=15

[cantfind1]

yes true, didn t read that bit but the point is it flows back to the tank to the siphon system and if you haven t got much flow back then the siphon system will be less efficient.

[cslnutta]

BMW seems to think otherwise.
Check pipe number 3 in the diagram.

http://www.realoem.com/bmw/showparts.do?model=BL92&mospid=47621&btnr=16_0484&hg=16&fg=15

Please keep this going guys, this is getting very interesting:thumbs:

You guys are obviously very knowledgeable, please continue to bless us mere simpletons with your plethora of info!

Fascinating stuff

[DuncanR]

I love all our technical discussions ESP when NZ_M3 and The Gorilla are involved.

Trouble is I am not clever enough to understand who is right everytime :bigcry:

+46 of us !!! :hahaha:

[shimmy]

ignoring the fuel starvation on RHD crners at 1/4 tank fuel, i think the fuel system is the root cause of the high temps at 100% throttle on hot days that i and others have experienced. Even FLOW got a bit at ZOLDER.

could the fuel at 100% THROTTLE be running short and running the engine lean and therefore hotter thus affecting oil temps and eventually water temps?

[shane@mbtech]

ignoring the fuel starvation on RHD crners at 1/4 tank fuel, i think the fuel system is the root cause of the high temps at 100% throttle on hot days that i and others have experienced. Even FLOW got a bit at ZOLDER.

could the fuel at 100% THROTTLE be running short and running the engine lean and therefore hotter thus affecting oil temps and eventually water temps?

I had zero issues Shimmy and I stayed out for approx 10 laps on the trot at full throttle. My oil temp and coolant temps ran far lower than yours did. Yours has a new engine, which for me points to external cause.

I had the fuel starvation at 1/4 tank of fuel too.

Unless you need a new fuel pump I doubt it is that. Have you tried a new fuel pump or even a fuel filter?

Other possibilities....... radiator
oil cooler
sticking stat(oil too)
restriction in cooling system

[AlexGTT]

I had zero issues Shimmy and I stayed out for approx 10 laps on the trot at full throttle. My oil temp and coolant temps ran far lower than yours did. Yours has a new engine, which for me points to external cause.

I had the fuel starvation at 1/4 tank of fuel too.

Unless you need a new fuel pump I doubt it is that. Have you tried a new fuel pump or even a fuel filter?

Other possibilities....... radiator
oil cooler
sticking stat(oil too)
restriction in cooling system

Shane, I'm totally convinced the issue is radiator. I had a similar slight rising temps at a very hot Donny the other day. However, oil temps stayed beautifully under control. That didn't happen before the bigger oil cooler went in. The oil temps would rise with water temps with the standard oil cooler.

The issue is, I'm sure, old stuffed up water rads. Not just external blockages (flies and shite between the fins, etc.) but internal build up which reduces the efficiency of the rad. 99% of the time the heat generation is handled but on track with compounding heat build up @100% throttle on a hot day and the heat gradually overtakes the rads ability to extract the heat.

If it was a fuel issue the lambda's and knock sensors would be going nuts and the ecu would pull things back timing wise, etc. Hence why the engine stutters on genuine 1/4 tank and less with fuel starvation.

I'm changing the radiator for a new oem asap.

[shane@mbtech]

Shane, I'm totally convinced the issue is radiator. I had a similar slight rising temps at a very hot Donny the other day. However, oil temps stayed beautifully under control. That didn't happen before the bigger oil cooler went in. The oil temps would rise with water temps with the standard oil cooler.

The issue is, I'm sure, old stuffed up water rads. Not just external blockages (flies and shite between the fins, etc.) but internal build up which reduces the efficiency of the rad. 99% of the time the heat generation is handled but on track with compounding heat build up @100% throttle on a hot day and the heat gradually overtakes the rads ability to extract the heat.

If it was a fuel issue the lambda's and knock sensors would be going nuts and the ecu would pull things back timing wise, etc. Hence why the engine stutters on genuine 1/4 tank and less with fuel starvation.

I'm changing the radiator for a new oem asap.

Thats my thoughts too Alex, but I dont have the rising oil/coolant temps. I will wait until I do.

Forte do a great coolant degreaser type product, used it only today on a car which had a failed water seal dumping all oil into water, and vice versa. Works a treat, its worth a try before taking off rad, esp for people who have to pay to get rad changed.