schadenfreude

Hey guys,

Took my car to the dyno today and thought I'd share my results. The car is a 1988 model, but not an S. I did a baseline run a couple of years ago with the car stock (apart from a 993tt BOV) and ran 197rwhp, with the air/fuel going into the 10s up high. I've since made the following mods:

* Vitesse chips, with FQS at position #1 and 3 bar FPR
* Accuboost with cycling valve deleted
* Tial 38mm wastegate courtesy of myswiss
* Cat-back 3 inch SS exhaust done at a local shop
* vdo boost gauge teed off the KLR line, reads 15psi in 4th gear (stock reads just over 2 bar absolute)

Doesn't appear to be any major vacuum leaks, stock gauge reads at 0.4bar or just under at idle, which equated to 16-18 in Hg when I had another gauge in there (vdo gauge is boost only).

Anyhow, today took the car for a power run and it made 222rwhp, which seems very low based on other's results. According the dyno operator, from when it hits full boost onwards, the AFR is into the 10s which seems to be robbing me of some power. One thing that is odd is that the boost readings from when it was on the dyno peak at only 13psi - disagreeing with the two in-car gauges. The red line is meant to be my baseline run, however it seems to disagree a little with the printout that I kept (at http://members.optusnet.com.au/~hugheskj/dyno_stock.jpg)

Air/fuel is apparently perfect when in closed loop mode, but goes super rich at WOT (explains the oil consumption, my rings are probably being eaten away) Any ideas as to why my car is so rich? Obviously the boost is a little low, should I crank it up a bit so it reads 17 on the in car gauges?

Rob

fast951

Rob, with the AFM if you run low boost at WOT it'll run rich. What is the "correct" boost you were running? 222rwhp at 13psi? Before turning up the boost, determine the exact boost...

Double and triple check for leaks, correct fuel pressure etc... Don't assume they are fine.
Check BOTH fuel pressure regulator and fuel dampner for any leaks.. Remove the vacuum line from each and check for any fuel.

Report back.

KuHL 951

Were you hearing knock at the initial FQS setting of 4? I thought FQS 1 was for retarding the spark a bit if local gas isn't up to at least 91 octane (US). I run 16psi (FQS-4)with mine on my AFM chip (91oct) and A/F is good; I could notice a drop in power at FQS 1 when I first installed the chip. I would think the 26/6 and 26/8 chips are set up proportionally the same. It's been awhile but I hope I don't have those FQS settings backwards in my head!

schadenfreude

Thanks John... I don't blame your chips as my car has always run a little rich, just now it seems to have gotten worse, probably due to the low boost. According to the dyno shop I'm running only 13psi in 4th gear... but according to my in-car gauge I'm running 15psi in 4th and 16psi in 5th. Which I'm guessing means either

a) The calibration of both my vdo gauge and stock dashboard gauge are out by 2 psi, or
b) The dyno guys introduced a boost leak when they tapped into the manifold to get a reading, or
c) The calibration of their boost sensor is off

And I doubt its A or C since the stock gauge and in car gauge correlated OK when I did the baseline run 2 years ago. How much difference would 2psi make to the AFR, do you know? I'll have a check for leaks, and arrange to get the fuel pressure measured.

schadenfreude

Kuhl, yeah you have those settings backwards, I've checked my email from John which has them.

FQS 0 is default and is 'safety mode'. Settings 4 through 7 are retarded timing versions of 0 through 3.

I'm running 98 RON fuel which I think is equivalent to around 91/92 MON

KuHL 951

I knew I'd screw that up if I didn't look for that install sheet from John I have to admit though that my car runs so much better with the AFM chip than my old Welts. I used to seriously lean out above 5K well before I ran out of turbo...now it's on the rich side at initially at WOT when first hits full boost. The AFR stabilizes pretty well after that to 6K as boost tapers off a bit. I'm convinced all 951's run rich under boost as any of the 911 and NA guys are always telling us following us on our runs. At least I don't shoot flames like some of cars I've seen

RogueM3

John, if he were running your MAF and corresponding chips, he wouldnt have any troubles running on low boost would he?
What would you expect his car to put down (rwhp) with this 13psi?

Thanks very much in advance for any answers you can throw at me in a response.

-Richard

RogueM3

It looks like you made your 222rwhp pushing only ~10psi (according to the chart)..which doesnt really make sense as shouldnt you have made more power earlier in the curve where your boost did actually seem to hit the 13psi you mention, and which the dyno recorded?

Just trying to learn and I believe I am reading that chart right and the right side values are in psi and not indicative of any AFR values....

schadenfreude

Yeah, you're reading the chart right, it shows power and PSI. The dyno guy had a separate display for monitoring the AFR, which isn't shown on the printout, and told me it was reading in the 10s from around the 110km/h mark where the power curve starts going 'lumpy'.

Perhaps I should get an EBC so I can get a nice flat 15psi boost profile

schadenfreude

Also if you do the conversions, its hitting full boost at 3100 RPM, isn't that a little late?

hally

yeah looks like you need a boost controller for a dual port, such as an mbc or ebc. Accuboost doesn't look like its working too well with your Tial. Another alternative is to get a stronger spring for your tial.

TonyG

schadenfreude

Get the dyno shop to:

A) Print you a dyno chart that has rpms on the bottom axis

B) HP on the left axis

C) TQ on the right axis

D) SAE correction instead of the "shootout mode" which is non-corrected.

TonyG

schadenfreude

Well, as I'm sure you know, RPM is a function of speed (21.2 mph per 1000rpm according to http://members.rennlist.com/951_racerx/) and torque is a function of RPM and power. As for SAE correction, I went to look up the formula since the conditions are printed at the bottom of the sheet, but apparently SAE correction doesn't work very well for turbocharged vehicles?

Anyhow, here is how it looks when you calculate the torque and RPM: