Just started using HP Tuners - some questions

[PaulS]

Hi all - this is my first post here.

In May this year I bought a new Holden Monaro CV8 M6 (the Pontiac GTO in the States) with the GEN III 5.7 engine. A superb car, I love it!

The car has the following mods: Tubular headers (4-2-1) with a larger bore (3&quot exhaust system with the cats removed. I also have an enlarged air intake system, freeflow air filter, large bore maf to throttle body pipe, and a modified MAF meter supplied by 'CAPA' in Australia. The car has been on a rolling road and in standard form produced 285 bhp with 296 lb/ft torque at the wheels. After the mods the figs were up to 350 bhp with 350 lb/ft torque - so I'm very pleased! But now it's time to get the car tuned properly with HP Tuners.

I've been playing with HP Tuners for about a week now. First time I've done any 'software' tuning on a car so please excuse my ignorance and apologies if the same questions have been asked before.

I've had the scanner running and have logged several runs. I've noticed that my LTFTs are set permanently at +25%. So my engine is running lean and the computer is compensating by adding in 25% extra fuel? (25% extra injector 'open' time?)

When the engine goes to WOT mode, I understand that the a/f ratio has to move away from 14.7:1 towards 12:1 for max power. What problem is having my LTFTs set at +25% going to cause, when I go to WOT mode?

I've also noticed that, even with the LTFTs at +25%, the STFTs still bounce up to +12 now and again. Does this mean that the system has reached the end of the adjustment scale, and my engine is still running too lean in certain situations?

So how do I correct this? I assume I have to alter the MAF scaling some how? What chart do I edit?

Finally - the LTFT & STFT histogram displays. Now I assume that the table represents a picture of how the engine is operating under different load conditions, but the x-axis figures of 0.4 to 8.0, and the y-axis figures of 15 to 105 - what do these figs actually mean? Same question for the x-axis figures of .4 to 8.0, and the y-axis figs of 0.08 to 1.20 in the advance retard tables.

Thanks in advance!

Paul

[Chris@HPTuners]

yes a ported MAF will make your car run lean (and fueltrims go +ve), as a start try scaling the whole maf table up until your fuel trims come back around 0 to -5. Then you will likely have to modify various areas in the maf table util all of your trims are roughly 0 to -5. If it were me i'd put the stock MAF back on, a ported MAF can be tuned but it takes a while. Also, check you don;t have any leaks on the intake pipe between the MAF and TB.

You'll need to use the spark histograms to see where you are in the table to modify your spark, as changing your MAF curve will move the spark higher (further to the bottom of the table) in the cylinder airmass axis.

the histogram axis match the VE table or the spark table depending. the 0.4 tp 8.0 is RPM (/1000 to make it smaller) the 15-105 are kPa (VE table axis), the other one is the cylinder airmass (g/cyl) for spark tables.

Chris...

[PaulS]

The more I read on here, the more confused I become!

I put the original MAF back in, and reset the fuel trims. Been driving the car for about a week, and I've recorded every run.

The LTFTs histograms have dropped: At part throttle/low rpm conditions, the max I'm seeing is +12. Moving towards open throttle/high rpm, the figures drop down to around +1 to +3.

So my engine is running lean at part throttle/low rpm, but richening up when moving to open throttle/higher rpm conditions. The engine isn't actually running lean, because the LTFTs are correcting the condition. This has been caused by the mods on my car - the air intake, headers and exhaust - which has altered the VE table. Am I on the right line??

So what do I do first - alter the VE table, or the MAF table? Opinions seem to vary - some people say getting the VE table sorted first, is the best way to start. And I monitor my LTFTs (I want them to fall) as a measure of success?

MAFs - and the need to scale the MAF table. I did have a ported one fitted. As it is allowing more air through - surely the electronics should report that fact to the PCM, why does the MAF table have to be altered? Why did the 'ported' MAF (I believe it has standard electronics, but bigger 'funnels' each side) that I had fitted before, alter the LTFTs so drastically? They were stuck on +25.

LTFTs - generally they have dropped since re-fitting the original MAF, but they still vary, I've seen them drop to 0 now and again. With time/mileage driven, will they eventually stabilise?

Final question (for the time being!) on the histograms - default view is 'last value' but I need to use the 'average' figure to see how I'm doing??

[luv2spd]

Yes, the thinking now is to do your ve table first. Look at the post in the V8 Engine section about ve tuning using your fuel trims as a guide. Once that is done, you need to change the maf table to get the trims back negative like they were when you were done with the ve tune. Yes, use the average value for the histogram.

[bensvuss]

Hi Buddy, I am new to Tuning and HP Tuners aswell. But the value of this product far exceeds my expectations. Great to have you aboard, Like you I have a 2002 holden VUSS 5.7 auto, with all the engine bolt ons. Now running a maffless set up, this is my second created tune, as like you i originally retained the maff. Personal choice but i think the maffless set up is the way to go, it's more responsive and accelleration is smoother, but each to there own.

I would recomend that you disable your LTFTS, and tune your VE with using the short term fuel trims from histogram 4 using average values click the (A) in the tool bar which is next to last and count. I would do this because STFTS are the only trims that are learnt and can be reset.

Once you have got your VE closer you can then work on doing the same procedure copy paste special, to correct your Maff.

Hope this helps you out.

Reguards Ben