Tom's B6 Build Thread

[bhearts]

Because I didn't measure it. Never do.

What a better tool to determine pumping efficiencies though.

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[TominMO]

What a better tool to determine pumping efficiencies though.

I'm doing real-word road tests, to include slight hills, not lab tests where you can get constant but unrealistic readings; and anyway I have no way to record such measurements.

[Advancedynamix]

Many people use a vacuum gauge for real world comparison. It's an old school trick to set base ignition timing as well. Any car in the 80's or 90's that had one of those gimmicky efficiency meters had a vacuum gauge. You can do the same thing with a vacuum/boost Guage mounted in the car. It's great for hypermiling, or diagnosing a running problem.

[nitrofarm]

Many people use a vacuum gauge for real world comparison. It's an old school trick to set base ignition timing as well. Any car in the 80's or 90's that had one of those gimmicky efficiency meters had a vacuum gauge. You can do the same thing with a vacuum/boost Guage mounted in the car. It's great for hypermiling, or diagnosing a running problem.

Or to get the correct "Power Valve" in my Holley.

[ryanprins13]

Many people use a vacuum gauge for real world comparison. It's an old school trick to set base ignition timing as well. Any car in the 80's or 90's that had one of those gimmicky efficiency meters had a vacuum gauge. You can do the same thing with a vacuum/boost Guage mounted in the car. It's great for hypermiling, or diagnosing a running problem.

I like having a vacuum gauge. Helps me keep my speed much more steady on a freeway and helps a lot for 'hypermiling'. Also tells me if i have a low tire, a headwind/tailwind and its quick diagnosis for when my idle issues pop up again.


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[TominMO]

Yeah I know about using vac gauges. But I'm looking at the speedo during my MPG runs, to keep a constant speed up and down hills. For my purposes, that makes more sense to me.

[Flyin4stroke]

Where's the #'s

[Advancedynamix]

^+1

[TominMO]

OK sports fans, here's the situation:

Went and did the dyno run. Part of the process is a sniffer up the exhaust to monitor AFR. The AFR stayed flat throughout the RPM range, at around 14.5ish, so he didn't do any real runs, and charged me less than the full amount. (AFR should drop down to around 12.5 - 13.0 at WOT; this didn't happen.)

The operator said the fuel issue could be any of three things:
a. fuel pump getting weak
2. stock injectors not large enough for the new head
III. need an adjustable FPR

Talked to Matt about this, and he said that since the AFR readout stayed flat throughout, his bet was that the fuel pump is fine, and I should go with an adjustable FPR. He also said the injectors being too small is not the problem here. I have two of his adjustable FPRs, one in the Aspire and one on the Matthew B3, so I will rob that one and stick it on the B6. He suggested I use ~60 PSI to correct the issue. This will of course kill my fuel mileage for normal driving around, but at least I can adjust it to taste; drop it down to 40 for long trips, for example. BTW, Matt told me he had the same issue with his B3, and the solution was the same: bump the FP.

Unfortunately I cannot show you the graph today, because I have a Linux computer and my low-end HP printer (which also scans) does not have any scanning software for Linux. Sunday I will scan it into a file at a friend's house and post it up then, FWIW. I can summarize it here tho:
Torque curve was very flat, and slightly wavy: 80 ft-lbs @2250 RPM, 92 @ 4000 RPM.
HP curve was not flat but was very straight: 35 WHP @ 2250 RPM, 69 HP @ 4000 RPM.
AFR was very flat @ ~14.5 throughout the range.
For comparison, on Matt's B3, both peak torque and HP were 85 @ ~5500 RPM, and AFR dropped down nicely to 12.0-13.0 when needed.

Soooooo, tmw I will slap the adjustable FPR on there, and go play with it, and then schedule another dyno run. A disappointing result, but hey, I learned something. BTW Matt also said that the 8v B6 head can be hogged out to produce ~250 CFM, but for my application this is pointless, so he didn't take it that far, only 155.

Vocab for noobs:
WOT = wide open throttle
AFR = air/fuel ratio
FPR = fuel pressure regulator
WHP = wheel horsepower (as opposed to crank HP)
CFM = cubic feet per minute, a measure of airflow

[bhearts]

OK sports fans, here's the situation:

Went and did the dyno run. Part of the process is a sniffer up the exhaust to monitor AFR. The AFR stayed flat throughout the RPM range, at around 14.5ish, so he didn't do any real runs, and charged me less than the full amount. (AFR should drop down to around 12.5 - 13.0 at WOT; this didn't happen.)

The operator said the fuel issue that could be any of three things:
a. fuel pump getting weak
2. stock injectors not large enough for the new head
III. need an adjustable FPR

Talked to Matt about this, and he said that since the AFR readout stayed flat throughout, his bet was that the fuel pump is fine, and I should go with an adjustable FPR. He also said the injectors being too small is not the problem here. I have two of his, one in the Aspire and one on the Matthew B3, so I will rob that one and stick it on the B6. He suggested I use ~60 PSI to correct the issue. This will of course kill my fuel mileage for normal driving around, but at least I can adjust it to taste; drop it down to 40 for long trips, for example. BTW, Matt told me he had the same issue with his B3, and the solution was the same: bump the FP.

Unfortunately I cannot show you the graph today, because I have a Linux computer and my printer (which also scans) does not have any scanning software for Linux. Sunday I will scan it into a file at a friend's house and post it up then, FWIW. I can summarize it here tho:
Torque curve was very flat, and slightly wavy: 80 ft-lbs @2250 RPM, 92 @ 4000 RPM.
HP curve was not flat but was very straight: 35 WHP @ 2250 RPM, 69 HP @ 4000 RPM.
AFR was very flat @ ~14.5 throughout the range.

Soooooo, tmw I will slap the adjustable FPR on there, and go play with it, and then schedule another dyno run. A disappointing result, but hey, Ilearned something.

02 should correct for for fuel in the fuel trim on the ecu. Key word is should

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[nitrofarm]

I would get the AFPR & a Wide Band installed,tweak it. Then go back,but that's just me.

[TominMO]

02 should correct for for fuel in the fuel trim on the ecu. Key word is should.

Agreed; I guess the flow of this head was too much for stock fuel mapping to overcome.

I would get the AFPR & a Wide Band installed, tweak it. Then go back, but that's just me.

That's a very good idea. Not sure I care to spend for a good wideband (I have been happy with the Innovate MTX-L in my Aspire BTW), when just bumping the pressure as Matt suggested will do the job. If I don't like the AFR reading on the dyno result, I can adjust from it rather than buy a wideband, and get pretty close. (Probably I will buy the wideband at some point tho.)

[Advancedynamix]

02 should correct for for fuel in the fuel trim on the ecu. Key word is should

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Nope. L jetronic based systems go open loop at WOT.

[Advancedynamix]

14.5 afr should still make good power. Mid to high 13's are the sweet spot for a modern fuel injected n/a engine unless it's horribly inefficient. You don't want your N/A econobox running in the 12's unless your compression numbers are 11:1 or higher or your fuel quality is on par with the swill they sell south of the border.
With a flat 14.5afr I would be suspicious of your tps. Looks like it's not seeing WOT and it's staying in closed loop, which will do it's best to keep that 14.5 target. Check that your WOT switch is working. Also, you should have had your cover plate popped off the VAF so you could tune that while your on the dyno. Funny that Matt never mentions the most easily tuned component on the system.

[Advancedynamix]

Also, tuning your AFR on a non load bearing dyno is like bringing your surf board to the public pool. Engine fuel trim is highly dependant on load. If the dyno cannot replicate the cars load, then it can't be effectively used to optimise your tune. Does that dyno jet have the eddy-current option?