MarkRobinson

Hi Guys, as suspected, I ran out of time to finish installing my fuel computer, and had to run raw with just my exhaust & chips:

282rwhp/276rwtq @ 11.4:1 Air/fuel through most of the curve. Could have easily broken 300rwhp with about 3-4psi less fuel on stock injectors...gotta get that controller dialed in!

Anyway, two most interesting cars were my friend's F355 making 318rwhp/222rwtq with Tubi, and another F355 making 308rwhp/232rwtq (with gutted cats & stock exhaust. Funny, the Tubi was much smoother & quieter than the stock system which was painfully loud with the gutted cats.

Mark

Warren928

Sounds like a good run!
Let us know how the AFC-R works out. I would be interested in how your settings on it affect your rwhp once you are dialed in. I like HKS products and would be interested in setting that up in my shark.
Are you running the x-pipe with high flow mufflers?

MarkRobinson

Hi Warren,

Here's my chart: this is my design, with my X-configuration, 4 high-flow mufflers, & AA chips. I hope this posts large enough to read.

AFC WILL work as soon as I figure out the proper voltage configuration: will call them once they open.

Mark

heinrich

That's pretty good eh? Those 85/86's can be developed quite well What's tubi?

MarkRobinson

You can see why we lifted on the first run: MAF peaked at 100% & the mixture shot lean as it has been: interesting, barely no difference between 3rd & 4th gear runs on the dyno: which is why I RARELY do 4th gear runs when tuning: more time for things to go wrong if you're tuning on the edge (though my tuning is conservative).

If you look at the lean flat between 3500-5, it's ideal for buiding HP & Tq, but if you lean out your fuel pressure so that you can break 300rwhp, you lean out the 3500-5k range as well, loosing your torque's fuel ratio to a dangerous level until 5k when it starts to pick back up. I'll be contacting AA as well, see if they can make a custom set of chips.

Mark

mark kibort

we have never seen fuel curves like that. its not true that you will gain HP on a lean condition. (or even leaner, unless you are way rich) we generally see 12.4 to 13.1 on most engine that run well and have top power. my 5 liter part euro made 293 with an AFM!!!! (12.5 :1 fuel to air ratio, and was flat from beginning to end AND, at the very end it started to go lean to 13.1, but that was at 6200rpm ) the difference between 12:1 and 13:1 was only a few hp when tuning. generally, we only changed things to not waste gas, and make sure we were not in the 13:1s for the ratios. many stock S4s run at near 14:1 as thats how they are set up at the factory for some of their curves. its not best for power, and certainl run the risk of one cylinder being at 14.7 stoich. where bad things can happen. thisis why most put on regulators to fight the stock leaness situation)

those curves you have from the chips seem pretty shakey. should be a lot flatter!!
see my holbert runs on the holbert 928 racer page. posted, is the dyno runs with fuel air readings.

mk

mark kibort

so, run 02 is stock computer and whats the A/F scale? is that 12:1 at 6krpm ?
what is the scale on the graph?
If so, is that 14.5:1 for the flat curve near 4k?? if so, thats not where you are going to build any hp or torque, its where you burn pistons or valves.
best power is in the 12 s best fuel economy is at 14.7:1, but at low power settings (ie cruise)


MK

MarkRobinson

Tubi is an Italian exhaust MFGR for Ferrari & Lambo's (Primiarily).

13.4 AF on my 928's has usually produced the most power. My red car started very rich, we leaned 1/2psi at a time & got about 4-5rwhp for every 1/2 psi leaned out. Went from 282rwhp to 302rwhp by the time we were done (1999). Dyno did not have AF readings at that time...so have to do-over. This fuel curve is typ. for '85-86 cars as all three I've dyno'd had very simliar curves.

Here's a better graph: TOTALLY missed that I cut off the air/fuel range on the left.

Mark

mark kibort

Thanks. thats an interesting curve, as you can clearly see the effects of the ratio going lean, and through 14.7:1

you may have leaned your fuel pressure .5psi at a time and went from 282hp to 302, but ive seen many dyno runs where nothing is changed and this kind of variation is made. also, if you see your runs below, the 13.5 vs the 12.5 points didnt change the curve at the same rpms, for different runs.

anyway, its pretty optomistic to think that you will always get 20hp for going from 12.5 to 13.5 :1 fuel air ratio. in fact, my engine, which was pretty close to the 85 US, but with the US Ljet injection, ran only 3hp diff by optimizing at 12.5: 1 coming down (richer) from 13.5:1 . generally, most all engines make best power and safest power in the range of the low 12:1s.

However, as you said, you didnt even have a/f ratios to look at and were just adjusting for max power, which means you could have been Way rich as you say, and definitey going from 9:1 to 13:1 can buy you that kind of HP. and that kind of hp on the lean to rich side, is even greater, MUCH greater.

nice graphs, they do tell a lot

Plus, interesting to know about the ferarri 355. always wondered about their ouput. 318h at the rears?? sounds about right! (apprx. 375hp flywheel with exaust)

Mk

Mk