Fuel starvation in tight left corners - solutions anyone?

[MonsieurX]

As usual, i take my Atom to Chambley which is a technical - testing circuit. Impecable surface, good grip and some tight corners. The circuit is also counter clockwise. While i dont have any issues for the most part, there are 2 corners where i can't get the power down whether im in 2nd or 3rd gear.

The turns are left handers, one is a U turn (kind of like the source in Spa but half the diameter) and the other is a 90 degree wide turn.

2nd gear is kind of useless in these corners except the U turn but i get the same issue as on 3rd gear - the throttle is 2/3rd of the way down and im waiting waiting for the power to come. It comes much slower than usual until the 5KRPM mark and then it bursts again - which is also when the curve becomes straight.

The tank was about 1/3 to 1/2 full when this happened.

I know it's not good to starve the engine....

This happens to a AA3 300 and my venerable AA2 245.

How can you solve this issue without having to do 3 runs and fill the tank again?

Thanks for any input...

[smokin]

A couple of suggestions, neither of which I've tried

1) A swirl pot powered by a low pressure pump. DT have a few options http://www.demon-tweeks.co.uk/motorsport/fuel-swirl-pots-collectors

2) Baffle foam or balls in the tank. Much simpler but not sure how effective and may effect that super accurate fuel guage  http://www.demon-tweeks.co.uk/motorsport/fuel-tank-baffles

[toms]

Worryingly, this sounds more like oil starvation to me, the VTEC dropping out/holding back......

What grade oil are you using Monsieur?

[Monza]

oil grade ?
oil mark ?
oil level on your dipstick ?
pics of you dipstick ?
this should not happen on an Atom 2 with Baffled sump, with good oil and and good level on the dispstick !

[MonsieurX]

Im using Motul 300 15w50 (as you recommend Monza)

Oil was changed 4 race days ago (not even half of the usual track days per year)

Oil level was at the top hole of the stick - checked twice before the day.

Am i turning too violently?

[Monza]

So only 2 possibilities (any other idea Tom ?) :
Baffled sump from factory or other ?
pics of your dipstick ? and take the length from the bottom of the plastic end of it till the superior oil level you rich and tell me.

For information, my brother with his Atom 2 300 never has this problem neither other "fast driving" Atom 2 that i know (running with this Motul, factory baffled sump and good oil level) and i didn't have this problem myself when i had Atom 2.

[MonsieurX]

The sump is baffled (apparently a better baffle setup than factory - i know this is questionable but this was specced in the engine rebuild since it was a concern)
Picture of the stick coming later (with a ruler next to it - csi style)

And Xavier has the same issue in his AA3 300... Same corners... And we drive about the same lap times...

I dont have this issue in Spa... So it might be the circuit's corners... Could it be? One turn is after a long straight with a hard brake zone, the other turn is after a slow left-right-right-left-left (all hard turns where you can't put the power down until the last turn). No brake-drifting involved (except a bit of powerdrift coming out)

[Monza]

Atom 2 and Atom 3 has different engines and sump, so no direct comparaison to make.
I don't know if Xavier C. has modified his dipstick (see french forum) on his Atom 3 and so run the good level of oil.

Waiting for the measurement of your Atom 2 dipstick.
The corner can , of course, be a difficult one for the oil but again on an Atom 2, with good oil level (and good baffled sump) it should not be a problem.
You are not running slick tyres ?

[toms]

I'm at a loss i'm afraid - but i'm sure this is oil starvation making the VTEC drop out, which is bad.  You should not have this problem, no matter what track - though from memory left hand corners are more of a problem on the Atom 2 due to the position of the oil pump pick up (which changed on Atom 3).

From experience of an Atom 2 endurance racing on slick tyres, extreme setup, pro driver - no problems with the factory baffled sump with either 10w/40 Magnatec or 10w/60 Castrol Edge.  0w/40 oils or low oil levels usually cause big problems, but that doesn't sound like the case here, though never tried the oil you mention.

I have no idea which AA3 you mean, does that have a baffled sump and what oil?  And is it topped up to the max?  The oil pick up system is totally different on a 3, so you aren't comparing like for like.  If that gentleman has a problem it would be best to contact the factory/dealer, rather than ignore it - an engine is a very expensive fuse!!

You can try 10w/60 Edge as a known starting point - but I suspect that your 'better' baffled sump might be an issue....something isn't right for sure.

[MonsieurX]

Thanks for the inputs guys. I'll check the dipstick and datalogger oil pressure to see.

My sump is alloy baffle with "doors" - the original wasn't baffled enough according to Komotech. So i made sure to get the right stuff for the engine rebuild.

I do not run on slicks... 888's...

[John Scherrer]

You need to measure / record oil and fuel pressure as this will tell you the real answer

Sounds like you have a way of seeing the oil pressure via the datalogger. 

[Monza]

you don't need because real answer is oil pressure. 

[MonsieurX]

Monza, the real questions i have are:
- what should the minimum pressure be?
- how to solve this issue (without overflowing the oil which can cause bubbles and froth at high revs - hence low oil pressures)

If anyone can answer this:
- what's the normal oil pressure in bars at idle?
  Mine starts at 6 and drops to 5.x after the pseudo choke goes off...
- what's the bar pressure at 5000 RPMs while car is sitting still?

After a big session i noticed earlier in the year that the pressure would drop to 2.5... Probably because oil is hot and still in the engine...

I need to find the exact factor multiplier for the datalogger... I guestimated it... so im kind of unsure im getting the right readings from the oil P. sensor

I've also had a situation in Spa where the oil was not there anymore on the stick, waited 30 minutes but oil didn't come back. Added a 1/2 liter just in case and still no oil on the stick. After a day of cooling, the oil was back at the right level...

Also noticed some soot by the exhaust exit...

[Monza]

before beginning to ask new questions, give clear answer to the ones i have asked you.
I don't want to beginn again a discussion as the one last year when the oil "disappear" of your engine ...

So, waiting for pics of your dispstick and lenght from the plastic end to the maxi oil level you use.

[MonsieurX]

Naturellement!

I wont be able to post the picture until Saturday though... Stuff to do (including building a Moog synthesizer)...