VR4 max boost on standard turbos??

[Nutter_John]

Yep your right ben it is from the standard uk spec 260 map , withdrawn via my new openport 2.0 thingmabob

[Turbo_Steve]

Have to confess, I've never really taken much interest in fuel cut.....usually at that point the ECU is going in the bin...it's only recently with factory flashing that this becomes a LOT more interesting.

[AderC]

PS, nutter, that must be a 260 table right? 230 is pretty damn low.

Cheers,

Ben.

If you thought that was low check out the VR-4's equivalent....



aDe

[Davezj]

yeh interesting stuff.

it is a shame that i can't add a second set of injectors to deliver more fuel. i could do a water injection system as i came across a really good install and write up with all the stuff required to do it. but it was on a 5.0L V8.

[Davezj]

is the load a changable peramiters in the Mh7202 ECU

[Nutter_John]

If it is in a table and has been defined in the XML then there is no reason why you should not be able to offset the load to a higher zone , but this would need to be test on a dyno so you can move the load cell around and make sure you are still very safe

They have left it low for a good reason that we don't know

[miller]

Whos brave enough to push those 100% figures into the 200's!!!!

[Nutter_John]

will not need to got that far mike , high 100's may be enough for stock

shame i don't own a vr4 anymore as i would have done it by now

[Kenneth]

once I sort out the high knock count my Galant is already showing, then ill give it a go. I even have a MH7202 ECU here which has those re-written, as well as some mods to the high octane fuel maps.

IIRC the VR-4 load scale is only mapped up to 200, so that will be max. I think I set it to 190

[Nutter_John]

Yeah Ken your right it is only mapped to 200 load ( which is roughly 1 bar ) so to increase beyond 1 bar we need to rescale all the maps to 230/240 ish

but pushing the load cell area to 190 will be around 0.9 bar ish

[miller]

Im gonna whip my ECU out and check the numbers..if it can be flashed im thinking a Eurospec visit may be in order!!

[Eurospec]

The boost cut table is interesting.

100 load very roughly equates to 100kpa- ie atmospheric and therefore 0 psi boost.

Most fuel cut heuristics also have a time dimension. I know not if this is in the code or if its in a definable table.

For example, when you configure cut in a standalone you do so by setting a peak load and an ammount of time that this can be exceded for before the cut.

I would suspect that the same occurs in a stock ecu.

The interesting point is that the heuristic must recalculate on each rpm zone. So lets say the cut time is 2 secs and the table looks like this:-

3000 120
4000 120
5000 150

Even if load exceeds 120 at 4000rpm if it stays in there for less than 2 secs then it wont cut. So you could run say 150 load accelerate like hell through 4000 rpm in less than 2 secs and then stay in 5000 for as long as you like at 150.

This theory would explain why we see some cars that boost cut on the dyno (where the acceleration rate is controlled) but yet dont do it on the street, and also visa versa where you set up a car in 3rd on the dyno and get no cut, yet in 4th or 5th where the acceleration rate on the road is much slower you do get cut at the same boost and rpm.

Cheers,

Ben.

[Nutter_John]

on the Evo it is defined as 1000ms , so if we can find that zone in the vr4 table you can adjust the time offset

[Mark 4]

That is a brilliant explanation Ben, thank you very much.

[bradc]

Which is one second in case people can't multiply and divide.

Being over 1 bar for a second doesn't happen often in a VR-4 in the lower gears which is why boost cut only really happens in 3rd and above. You could just add an extra 0 in there and make it 10 seconds

[Nutter_John]

Your a numpty Brad

The values are absolute so 100 kpa is normal atmosphreric pressure , 200 would be 1 bar

[bradc]

'You're a....'

[Wodjno]

The boost cut table is interesting.

100 load very roughly equates to 100kpa- ie atmospheric and therefore 0 psi boost.

Most fuel cut heuristics also have a time dimension. I know not if this is in the code or if its in a definable table.

For example, when you configure cut in a standalone you do so by setting a peak load and an ammount of time that this can be exceded for before the cut.

I would suspect that the same occurs in a stock ecu.

The interesting point is that the heuristic must recalculate on each rpm zone. So lets say the cut time is 2 secs and the table looks like this:-

3000 120
4000 120
5000 150

Even if load exceeds 120 at 4000rpm if it stays in there for less than 2 secs then it wont cut. So you could run say 150 load accelerate like hell through 4000 rpm in less than 2 secs and then stay in 5000 for as long as you like at 150.

This theory would explain why we see some cars that boost cut on the dyno (where the acceleration rate is controlled) but yet dont do it on the street, and also visa versa where you set up a car in 3rd on the dyno and get no cut, yet in 4th or 5th where the acceleration rate on the road is much slower you do get cut at the same boost and rpm.

Cheers,

Ben.

That explains why i always got fuel cut on rolling road days

I had to decrease my boost level to around .8 bar, until RPM was over approx 5000rpm then the boost could be raised as the time the car was in each RPM range above 5000rpm, must have been lower than that set in the table..

BAh !! Rolling roads You gotta love em amd you gotta hate em