Mafless part 1

Thanks to Michael Clark for helping fit the Pacemaker last week.

After fitting the exhaust I was logging fuelling and spark. No issues with spark. But I noted O2 was running lean around 2000rpm then from 4000rpm on.

Hmm, so to adjust the maf flow air model, or do things properly and tune the virtual ve polynomials first.

Well it didnt take me long to decide to go straight to mafless. I know I need to remove the maf due to the potential restriction it represents. But stage 1 was to leave it in place and just fail the maf in the ECU.

This basically entails telling the ECU that any response from the maf signals a failure, rather than the default extreme values etc.

Still losing 5kpa air pressure somewhere, but at least now the tune is in place to allow maf removal without issue.

So first logging showed fuelling to be out by 7% over around 3500rpm and much the same at lower RPM.

Fuel variation from VVE

This makes sense that most gains are at the upper RPM range. So next is to check throttle is opening properly under throttle and remove the MAF..

..Yay, mafless, BUT!

kpa still reads off 4kpa! Well I was told that would be the case. But seeing is believing.

So maf can go back in, though now its tuned mafless, maybe it will remain out to allow for future changes.

Geway, a fellow Kiwi, who has a ported LS3 and throttle said he was running 100kpa at WOT with a large cam. Given the MAP sensor is located right behind the throttle Im going to need to look at that. Indicated throttle is only 83% the VXR8 shows 88% so Im now wondering if the throttle is fully opening.

I would not have thought the throttle or intake were a restriction stock. Logic says the throttle is not opening 100% so thats the next port of call.

So in summary now mafless, but no new gains other than from the exhaust and adjusting the base tune to take the exhaust changes into consideration.

Also because I have now thrown a spanner in the airflow model, all future calculated torque numbers will only be relevant to this new baseline. So Ill have to go to Surrey Rolling Road for a proper comparison.

Quick update with results..

So some improvement. Logged 450ftlb today compared to 400ftlb on the original dyno pull. Now Im not losing any timing so thats good.

However I am losing 4 or so kpa still despite the new intake. Thats a bit sad. However as the intake pipe is 90mm and a certain piece of junk is 85mm with a mesh and air blade stuck in the middle of it. I think Ill be fitting this piece of equipment pretty quickly!

I actually have a black piece which in theory should fit exactly where the MAF is at present. That will be going in ASAP to help look into the missing air pressure.

I cant imagine its the intake as they are supposed to flow around 320cfm much the same as the heads. In theory that should be good for around 600fwhp. Stock; the engine is nowhere near that. I suspect Ill gain a couple of kpa from removing the MAF. We will see.

So anyway here is the latest Dyno Log run.

Spark timing was recovered via some gentle ECU tweaks. Thats a 12% torque gain tune only in effect. BHP is also up about 8% over the original pull. But I think there is another few percent of easy gains from sorting out the missing intake air pressure.

Once thats found I might try some 97 octane or even shell 99 as Im running on standard 95 RON at present. I actually had to take about 3 degrees or so out of the midrange as the OEM tune was knocking constantly at cruise believe it or not! 

I guess HSV think that running up against the knock limit and pulling timing constantly is a good idea. Not sure why! Near on 10% gains to be had by avoiding knock and reducing timing! It was the same story with the LS2. I made more power with less timing. Perhaps part of the problem is getting 1*C intake air at load on open roads in Australia!

Forgot to also mention gains were also had from changing fueling a tad. 

A fellow VXR8 owner with ported intake and throttle said he gets near 100kpa with the MAF. So thats very sad. Suggests the issue lies with the intake or throttle. Thats a bit harder to cure. Ill see what happens swapping the MAF out. It might give me one or two kpa. I can then console myself that all is not lost.