Headed to the dyno

[Gman7007]

Awaiting UPS to deliver a Walbro, install it in the 10AE, and then head to the dyno on Tuesday. I do not have a wide band nor a bung welded in but the shop said we could use the rear O2 sensor position for the runs.

Question: Should I factor in the .5 A/F “correction” like people do when you get a tailpipe reading?

Jose

[Tom @ Fast Forward]

The SAFE thing is to still shoot for around 12:1. The 0.5 offset could be only 0.1 or 0.2 depending on the state of your cat. Worst case if you shoot for 12:1 is that it actually might be 11.6. That is not a bad thing.

[Gman7007]

Well the shop did not use the rear O2 bung, instead clamped their wide band sensor to the tailpipe. I do not put much faith in that. Car runs fine but it "reads" avg of 13:1 at the tail.

Will any readings be off if the shop has the "altitude" set at 4500 ft? I do not know of any location in Florida that high:excl:

10AE results: SAE Corrected 180 HP 151 TQ

Anyone have any experience with Innovate Motorsports LC-1 and the DB gauge? Looking at buying a pair.

[Tom @ Fast Forward]

Tailpipe O2 is typically ~0.2 leaner than an in the pipe pre-cat O2. If it is reading 13:1, I would run with real caution as you may really be lean.

[FormerDatsun510Man]

13:1 is too lean, even post cat. It is barely rich enough for a fine-tuned normally aspirated setup. With boost, you are asking for trouble running that lean IMO. I suggest that you turn the PC Pro and E-Cool up a couple lights (making note of the original settings) until you can get back to the dyno and have it properly running 12:1. With it currently at 13:1, even without knock, you can still end up putting holes in the sides of the pistons if you try to race it at the track or do extended running under boost. For short bursts, without knock, you are probably ok, but I would still fatten it up to 12:1. Even 11.5:1 is fine and doesn't seem to make much impact on rwhp. Remember, it is far better to be a little bit rich than a little bit lean.

Bill

[Gman7007]

Agree. That's why I am shopping for a wide band set up. Attached was the last run with the following settings.

yel/blu 8
red/blu 8
grn 1
yel 1
red 4

It helped above 5K.

I have since adjusted

yel/blu 8
red/blu 8
grn 2
yel 2-3
red 3-4

BTW, No e-cool in my set up.

[Tom @ Fast Forward]

If you know someone with a fuel pressure gauge, check yours under load (WOT up a hill, for example). You may be losing pressure. We had a 96 in here that had an A/F curve just like that when we did the base run and it was stock. We put on a new Walbro fuel pump and a new FPR and his stock A/F was a perfect 12:1 from about 3000 and up.

Your up turn at the end looks like you are running out of fuel. If it were ignition, the HP curve would have tapered off.

[FormerDatsun510Man]

Based on your settings and that attached run, my guesstimate is that if you ran the R,Y and G all at 4, you would have a a/f ratio that would start at 13:1 at 3000rpm and it would fatten up to 12:1 by 6500rpm with it then starting to lean out again. I would start with those settings at minimum to keep it rich enough. If anything you might even want to run the settings of G-6, Y-5, and R-4 to try and keep it closer to 12:1 all the way through. By the way it leans out after 6500rpm it does look like you are likely running out of fuel, do you have the Walbro installed?

Bill

[Gman7007]

Installed the Walbro just prior to the dyno runs.

I'll rig up a fuel pressure gage and make some WOT runs.

[Gman7007]

Finally installed the AEM UEGO today. As I suspected the dyno shop’s tail sniffer was reading a bit leaner than the car was actually running.

Did a couple of runs up to 7000 and I am safely below 12:1 the entire band. Did not have a copilot to read more accurately but we’ll get to that tomorrow and tweak as necessary.

[CRYPTiC]

Finally installed the AEM UEGO today. As I suspected the dyno shop’s tail sniffer was reading a bit leaner than the car was actually running.
That is in line with my (limited) experience. Someone did an experiment with two WB sensors and noted 0.5 AFR difference pre-cat and tail pipe.