19 replies to this topic

[TV5RR]

Hi all, Need some help . I'm doing some trackday with my vx turbo . My issue is that on kick left corner I have a loose of power at the ed of it . I don't really understand . With fuel tank full , nothing happen during 1/3 of the session . One session is 22 miles and 12L -14L of fuel . No answer from the engine when you push the throttle during 1or 2s (?) like an empty fuel tank . It doesn't happen on all left corner and never had any troubles on road . Any idea .... The vxt is remapped up to 7000rpm, (240hp said by the last owner but never checked ) , std intercooler, e85 fuel.

[CocoPops]

Fuel pump is on left hand side, so sounds like fuel starvation as fuel sloshes to the right in long left hand corners. Alternative is a pro alloy tank. (Speak to batman)

[Duncan VXR]

OEM fuel tank issue The pickup is on the pax side and not a fully baffled system Keeping more fuel in the tank helps or Pro Alloy tank upgrade with options of increased range Can pass on some discount if it helps? (15%) DG

Edited by Duncan VXR, 05 March 2017 - 08:13 PM.

[Nev]

Might be an electrical short circuit if a wire is slightly lose and "disconnects" or "shorts" during the turn?

 

[TV5RR]

Fuel starvation with only 6L less than the top is possible ?? I Was also thinking about electrical issue . The problem is that it's only on track . Thanks for answer .

[Acidpopstar]

It's defo fuel starvation. Happens on long left handers but you would only ever experience this on a track. Sent from my iPhone using Tapatalk

[P11 COV]

It's defo fuel starvation. Happens on long left handers but you would only ever experience this on a track. Sent from my iPhone using Tapatalk

 

But having used only 6 litres from a full tank....unlikely.

[Duncan VXR]

Crap in the bottom of tank / blocked filter, pump going weak, electrical connection Still sounds very much fuel starvation from tank but could be other things maybe? Check all the basics from connector of doom, impact switch, intake pipe, fuel filter Only really experienced the issue with oem tank but experienced issues with ever other item mentioned also 😁 DG

[Captain Vimes]

Very likely fuel starvation. I got it after just 7/8 laps on the triple left handed at Rockingham. Simple solution is to use a higher gear on the long left handers... https://youtu.be/xMYSlmy9w64

Edited by Captain Vimes, 08 March 2017 - 12:08 AM.

[TV5RR]

The problem come after I progress with an increase of 12 mph in the corner . The sequence is 175 km/h, at the entry, small brake (120km/h) to prepare the corner and full throttle to be at the top speed at the end ( 135km/h). What i don't understand is that I usually track the same circuit with my Elise s1 (150hp) and it never happen with it .(both with Oem fuel tank , Walbro 255L pump and e85 fuel). A friend with a vx atmo at similar speed has not any surge issue with his Oem tank, Oem fuel pump, and e85 fuel and could run up to little more than refil light .... At the end , i'm quicker with a less hp/tonne ratio car with similar chassis upgrade . Still septic about starvation with only 6L less

[C8RKH]

So if you're still not sure about the tank after the advice above and your friends experience then i guess it is the step by step check of the electrical connections and pipes until you rule that out and then are only left with the tank as the issue.

 

Let us know how you get on after the checks.

[Spitfire Engineering]

It's fuel starvation.

 

The canister is out of fuel the only question is why.

Maybe the canister is full before you start the corner and you simply are using all of the fuel.

May there is a reduced fill capacity because of the pump output lowering or crap stuck in the eductor.

 

Any changes recently? power? etc?

Fuel pump fitted? OE?

long term problem?

Time from initiating the left hander to start of starvation?

 

If you want to see where the fuel is during the corner you simply imagine the tank at an angle, so if you are cornering at 1G then you have 1G lateral and 1G vertical (gravity) so that is the same as the tank being at 45 degrees. Now you can see why the with just 6L gone it will be the 6L from the pump end not from the top of the tank down.

 

let us know and we can advise

 

 

[TV5RR]

The problem was noticed 2 years ago . I have changed and upgraded the fuel pump (1.5 year ago) for a walbro one 255L but it was the same issue . The fuel pump relay has been changed 1 year ago after fuel pump stop running .Problem solved . The big change is my driving . I have progress and win 2s with the Elise s1 this year as soon as I have understood I could pass there left corner 10mph more . When I decided to try the vxt at same speed ( then with more G force ) , the lost of power was highter and longer than 2 years ago and cancell all the fun. At the end : 2years ago : vxt lap 1'47"with small vxt loose of power elise s1 1'49" Now : vxt lap 1'47"-more 48" with big loose of power Elise s1 : 1'45.7" Thanks for all

[fiveoclock]

I had exactly this problem in a race at brands about 4 laps in with a full tank. Long left hander onto the GP circuit, get the power on on the exit and it cuts out, fires again after about 2 seconds. Solution for the race was use a higher gear, not ideal. Permanent solution for me was to fit the cannister/pump set up from Seriously Lotus that has a bigger cannister. Fixed it.

[fiveoclock]

https://www.seriousl...-fuel-pump-unit

[2-20]

Do you use E85 in your VXT ? E85 means more fuel cumsumption and it cannot help.

[Spitfire Engineering]

The problem was noticed 2 years ago . I have changed and upgraded the fuel pump (1.5 year ago) for a walbro one 255L but it was the same issue . The fuel pump relay has been changed 1 year ago after fuel pump stop running .Problem solved . The big change is my driving . I have progress and win 2s with the Elise s1 this year as soon as I have understood I could pass there left corner 10mph more . When I decided to try the vxt at same speed ( then with more G force ) , the lost of power was highter and longer than 2 years ago and cancell all the fun. At the end : 2years ago : vxt lap 1'47"with small vxt loose of power elise s1 1'49" Now : vxt lap 1'47"-more 48" with big loose of power Elise s1 : 1'45.7" Thanks for all

 

Good info, thanks

 

The Walbro fitted by itself will only make it worse so no surprise there.

The fact the pump relay packed up is no surprise either as the Walbro uses about twice the power of a modern turbine pump so if anything is marginal (poor contacts etc) then it usually compounds the problems.

 

The times I actually wanted was from starting the left turn until starvation, do you have an in-car video of this happening? or another car achieving the same speeds at the same circuit?

What is the total length of the time spent in the left hand turn?

 

In most cases the larger capacity fuel pump canister as mentioned above will help and may solve the problem, it is also fully E85 compatible and has the latest E85 electrical connector as well.

The new pump unit will give you about 20% more stored fuel but it is also very efficient at refuelling the canister, about 4-5 seconds from empty to full so you should be fully charged by the start of the turn.

As it can suck directly from the tank it also recovers after starvation much quicker than the OE unit.

If the engine is using a lot of fuel and/or the turns are long of compound left turns then the only solution will be a trapped tank as you simply cannot store enough fuel.

 

[TV5RR]

Yes e85 on each cars with the fuel pressure regulator modified for 3.8bar if I remember well . The problem was the same on petrol years ago.

[Spitfire Engineering]

I had exactly this problem in a race at brands about 4 laps in with a full tank. Long left hander onto the GP circuit, get the power on on the exit and it cuts out, fires again after about 2 seconds. Solution for the race was use a higher gear, not ideal. Permanent solution for me was to fit the cannister/pump set up from Seriously Lotus that has a bigger cannister. Fixed it.

 

Good to hear, Thanks

 

We have had continuing starvation problems with two cars that have the new unit, both are VX and both are heavy users and there is one particular left hander at Zandvoort which is both long and then continues left uphill, the video's show the starvation quite clearly.

 

The other 150+ units behave the same as yours, the extra 20% capacity along with the fully charged canister before the start solve all but the more extreme cases.

I assume the problems with the VX is the engines fuel requirements as none of the Elise S2 cars that have the same pump unit have ever reported anything to us even those with SC Hondas.

 

Gaz

[Spitfire Engineering]

Yes e85 on each cars with the fuel pressure regulator modified for 3.8bar if I remember well . The problem was the same on petrol years ago.

 

Exactly what rail pressure/boost are you running now?

Power?