Louie928

I'd lean toward going to the dyno. I don't know what your "cheapo" oil is. If it is good break-in oil then it's ok to use. Single grade, non-detergent or something is fine to use. If it is some of the $2 per gal reclaimed oil, then not. Take off your oil filter and check for metal first. You could do more damage by running it too rich during the few dozen WOT blasts you know you'll do on the highway waiting for 500 miles to go by than a few seconds at WOT on the dyno could do.

mark kibort

good point.
By the way, its penzoil off the shelf 10-40 weight. oil pressure is generally ok, until it gets hot, then its down about 1 bar vs my Amsoil tests at idle or 3krpm.

no redlining , but about .5 seconds at 5800rpm to do my 60-100mph run last night, fuel seems good, not too rich as there are two lights on my AF meter that its boarderline on. I was 12.5 to 13:1 with the holbert car. ive backed the fuel pressure down to 58psi from 72psi with the holbert car and have the 30 lb injectors.

what was that power formula for injectors vs pressure relationships?

mk

drnick

greg, thats interesting stuff about the differences between dyno machines. id been puzzling over why all the american 928s were so much more powerful than the rest of the world - could it be the cheap gas with lower octane??

Bill Ball

Mark:

You'll probably get more HP if you leave the 10/40 in for the dyno. Pull out the filter - cut it open to see what's inside.

I can come over any night this week and install the LC-1 with you, then go ahead and schedule the dyno.

The idle was initally hunting too. You have several extra switches wired in, including one for the idle switch. When you flipped that off and on I couldn't quite track the effect it was having. Normally, disabling the idle switch will cause the idle to hunt.

Louie928

That's good oil. When the filter stays clean of metal, dyno it.

Here is a formula for fuel injector sizing.
http://www.injector.com/injectorsele...e239c17f204cbf
Fuel injector flow varies as the square of pressure. That is changing pressure by a factor of 2 will change flow by a factor of 1.4. 928 engines are efficient so BSFC is around 0.45 at max power of 13.5:1 AFR, probably 0.5 at 12.5 AFR, and 0.4 at 14.7 AFR.

marlinspike

Been at my brother's place without internet. Finally found a hot spot. As someone who doesn't have the time or money for dynos and wide-band O2's etc, and simply learned to tune by looking at the plugs I'd say we need more photos showing the plug from every angle, but to me it looks like the mixture is good, you just need to go cooler on the plug.

AO

Genetics! You should know that...

123quattro

It's probably already been said, but you can't rely on a narrow band sensor to infer any A/F ratio outside of it being lean or rich. The signal output is highly nonlinear and it can't really see changes in ratio outside of just around stoich. Get a wideband in there. There is no substitute. Especially when they can be had for under $300. It's cheap insurance for a $10,000 engine. I keep them permanently mounted in my cars that need them.

mark kibort

we are going to do this , as its a good idea. I have got the narrow band readings down to be +/- a point or two. when its really round 13.5 the one light (blue) lights up. around 12 -13, the last light lights up. i think its in the healthy range, but im not going to bank on it until i see the dyno. (they have a wide band there)

as a note, my half throttle position is still faster than the ole holbert car was in 60-80mph runs. Im estimating 400 to 420rwhp.

mk

mark kibort

The o2 sensor was loose, by almost a full turn. now it idles fine.

the switch i have for the idle switch disable works more when the engine is warm. (using the 02 sensor). it raises the idle overall , but can hunt more if the idle drops for some reason. you can rev it though, and it doesnt fall flat on its face. I usually idle for long periods with idle switch active, but drive with it disconnected. much more smooth due to the higher idle in every way. Especially on the track.

mk

mark kibort

what do you think these guys are going to say?

Mk

hacker-pschorr

Where is all that smoke coming from?


Oh I'm kidding, you left that wide open!!!

Good job on the build, now get that sucker tuned!!!!!

mark kibort

Hey, Im knocking on wood! It seems to be running great. even , but high compression, no pinging, and a ton of smooth neck jarring power. I havent been over 5krpm, but next tuesday we will see on the dyno. I have about 120miles on the car now, just burned through about 40 bucks in gas driving around!!

Tunning will be mixture verification next tuesday, and hopefully, its healthy at 12.5 :1


mk

hacker-pschorr

I figured it was like "break a leg" or something

Bill Ball

When is this happening on Tuesday? We need a bit of time to get the WBO2 installed and calibrated.