quick MAF question

[mike74]

morning guys, a quick question for all the guru's out there. ive been reading through the MAF adjustment threads with great interest & was wanting to try it on my vr4. im obviously not wanting to lean it out too much for fear of melting something. ive got an AFR printout from last weeks RR day at wallace performance which im hoping someone can look at & give an indication as to whether it would be safe to do or not. im not wanting uber power gains or anything too silly, a slight improvement on my fuel consupmtion would be nice though. any advice would be greatly appreciated

cheers for now,

mike

33554

[evonut270]

morning guys, a quick question for all the guru's out there. ive been reading through the MAF adjustment threads with great interest & was wanting to try it on my vr4. im obviously not wanting to lean it out too much for fear of melting something. ive got an AFR printout from last weeks RR day at wallace performance which im hoping someone can look at & give an indication as to whether it would be safe to do or not. im not wanting uber power gains or anything too silly, a slight improvement on my fuel consupmtion would be nice though. any advice would be greatly appreciated

cheers for now,

mike

33554your afr plot seems fine although id keep AFR to between 11.5+12.id also get your boost control sorted as yours seems to have a nasty spike late on.why not just get it remapped ?

[elnevio]

Do you have any boost control at all? The boost peak just before 6000 rpm is unusual, although not a massive spike in the grand scheme of things (an increase of 2 psi over a range of 1000 rpm, which isn't exactly sudden!). Perhaps your dump valve is sticking a little bit.

Assuming everything is stock, the AFR is more than plenty rich enough, although I'd say it looks leaner than most VR-4 stockers. Nothing to worry about, but worth rolling roading when setting up a boost controller, to keep an eye on the AFRs.

[Turbo_Steve]

Something definitely isn't right there, and I wouldn't even think of touching the MAF given that boost curve.

It's possible that, as Nev says, it's a leaky dumpvalve, or perhaps an exhaust blockage.

Or that for some reason the ECU is pulling masses of timing in the midrange.

[Eurospec]

Typical vr4 fuel curve, although you dont want to take any fuel out top end. Boost curve does look wierd though. I know sometimes they do, but they aren't supposed to!

See if you can get that boost leveled out before touching the maf.

cheers,

Ben.

[mike74]

thanks for the advice guys. the chap at the rolling road said the boost curve was a little off but that this kind of thing was apparently quite common with OEM boost control. he suggested fitting a bleed valve or similar to flatten it off a bit & try to remove some of the spikes. the car is completely stock apart from a panel filter, including the exhaust. think i might just leave tinkering with the MAF for now. dont wanna toast the engine or anything else. ive got a bleed valve in the garage so i think ill get in touch with the rolling road again to get that installed & set up properly. ill get them to have a play with the MAF at the same time too & hopefully come back with a healthier looking set of graphs. thanks again for all the responses, you've probably saved me a frikkin huge repair bill /thankyou

[mike74]

oh almost forgot, whats the best way to test the dump valve? remove the vacuum pipe that goes into it & pressure it up with a foot pump?

[bradc]

We've seen quite a few in NZ do that, running below 10psi from 4000-5000rpm (or thereabouts) and then peaking above 10psi around 5500rpm and making quite a bit of power at that point, sometimes torque even goes up from 5000 to 5500rpm!

I wouldn't worry too much about it, lots of people are running boost above those figures, and I tend to agree with the rolling road guy, if you up the boost with a bleed valve the mid range boost will be drastically increased and the top end boost simply won't go up much at all because the turbos won't be able to flow much more.

[mike74]

hmm, even more food for thought....i had a wee re-think yesterday. rather than go to another RR, i reckon ill get a boost gauge installed instead so i can monitor things myself. at least then i can install a MBC at some point in the future & set it to about factory boost. had the car out for a good blast yesterday & payed particular attention to the way it felt while booting it. certainly couldn't feel boost spiking or indeed tailing off. the guy at the RR tee'd into the boost line with the red tip to it if that would make any odds to the graph? anyhooz, not in any hurry to mess about with things so will just do it slowly & properly! cheers for all the useful advice chaps, much appreciated :)

[evonut270]

hmm, even more food for thought....i had a wee re-think yesterday. rather than go to another RR, i reckon ill get a boost gauge installed instead so i can monitor things myself. at least then i can install a MBC at some point in the future & set it to about factory boost. had the car out for a good blast yesterday & payed particular attention to the way it felt while booting it. certainly couldn't feel boost spiking or indeed tailing off. the guy at the RR tee'd into the boost line with the red tip to it if that would make any odds to the graph? anyhooz, not in any hurry to mess about with things so will just do it slowly & properly! cheers for all the useful advice chaps, much appreciated :)if you need your fuelling checked drop me a pm

[mike74]

cool cheers for the offer evonut270, ill most definitely bear that in mind :)

[evonut270]

cool cheers for the offer evonut270, ill most definitely bear that in mind :)no probs.remaps are also available.