OK, the car is misfiring badly above 5000rpm so I took it to Weltmeister today to have it checked out on their rolling road, great bunch BTW. I am a little worried about the AFR, as you can see it's stupidly rich right across the board, the car has a micro fueler (seventh injector) to keep it in line at the top end, you can see it kick in at around 5000rpm. The car feels quite strong although it's clearly not putting out what it was when I picked it up from 9m. Could this rich condition and fouled plugs cause this kind of loss in power? The Weltmeister chaps over laid my run with another 930 which was putting out 510bhp to show me the difference

First my AFR's


The 9m run
https://rennlist.com/forums/attachme...d=132235&stc=1

My run at weltmeister with the other 510bhp 930



As you can imagine i'm a little confused, sorry if the images are poor i had to take pics and shrink them, i just can't work out how to shrink a PDF file

Hope someone has some answers

Cheers chaps

 

Anyone?

Some more questions

1) Am i running so rich that i'm going to damage something?

2) Could worn plugs and running too rich cause a 100bhp loss of power?

3) If i get the plugs changed and it's still running rich should i up the boost and/or go for a bigger turbo to make use of the extra fuel?

It's currently running with

Garrett BB turbo (not sure of the spec)
9m headers (similar to B&B)
1 bar spring (no EBC)
Ported heads
Ported intake manifold
965 Intercooler
7th injector
Ignition set at 29 degrees

What would you guys do?

Cheers for any help

Jonathan

 

OK - if it were my car, I would remove the 7th injector enrichment because (as described in this forum in the recent past) it does not deliver consistent fuel to all cylinders. The manifold is set up for air (a gas) and not fuel (a liquid, albeit in vapor form).

Yes, the extreme rich condition you have could be the reason for the low HP numbers (and could be the dyno, if its different from the base line dyno used - big differences between some dynos). In addition, you could be raising your EGT by pushing unburned fuel out into your headers and into the turbo. You might want to be careful of this as you could elevate the temp of the turbo needlessly.

In my opinion, based on my own experience in tuning my car, I like to have an initial AFR while building boost between 11.8 to 12.2:1, then bring it up to 12.5 to 12.9 under WOT. Anything below 12.5 is a waste of fuel and does nothing to cool the mixture. Remember, the most critical issue in these engines is heat. Important - the above numbers are based on my motor only and work very well. I not only monitor AFR now, but also EGT's for a complete picture of what is happening in the combustion chamber.

For example, I can run around town, no boost, with 36 - 38 degrees of timing with no problem. Once I add boost (high effective compression), heat QUICKLY (seconds) builds and promotes detonation - not timing. Look at our naturally aspirated cousins who can run 38 - 42 degrees of total timing with reasonable compression. Compression, whether static or induced (turbo), is what builds heat quickly (consider a diesel engine). In order to mitigate the heat issue in our motors, the most effective method is to reduce timing, not add fuel.

So, while you think about what you want to do, consider this during tuning. A one bar boost spring with the stock distributor shortens the life of your motor significantly because you have little or no control over heat management. Adding more fuel, as you are finding out, does nothing but defeat the idea of a high performance engine - actually, you are probably putting the fire out before it can do damage.

I would recommend that you re-install the stock spring to reduce the issue of heat building and possible detonation. Next, get rid of the 7th injector extra fueling, then take the car to the dyno and check the AFR's. Once you have a base line AFR and power/torque outputs, then decide if you need to go into the WUR for fine tuning. If you feel you need more power, then buy a good electronic ignition system where you can re-install the 1 bar spring and set proper timing. For example, at one bar, my car has 15 degrees (and approx 470 lbft torque) of timing where yours has something like 24.

Question - what plugs are you using. This is VERY important on these cars.

Good luck

 

Don:

What kind of fuel are you running if you are running that high of an AFR?

I know I run 100 octane all the time, and I never let mine go above 12.2-12.3. And I have lower compression than you do. So with your higher compression I'd think you'd need much better fuel???

Brian

 

Get your own AFR meter from Stephen.

http://imagineauto.com/Merchant2/mer..._Code=AFRGAUGE

http://www.innovatemotorsports.com/

This meter is excellent value for money. If you want to pay more go for Motec PLM1.

http://www.motec.com.au/plm.htm

 

Don thanks for all the info, it's good to hear it from a guy who's BTDT. Last year my car didn't have the seventh injector and was putting out too much power for the CIS alone so the ignition was backed off to around 32 degrees as a safety margin until we could address the fuel issue, I have attached a graph showing the boost pressure, I make it a little over 0.9bar so the 1 bar spring isn't giving 1bar anyway, do you think that's safe enough? Then as you can see on the AFR graph (this one is in Lambda but works out around 12.85 Afr at it's worst) so it was running too lean even at 32 degrees. The 416bhp shown is at the flywheel (est.) BTW.
I have read that the euro CIS is good for that even at stock ignition settings so either the dyno is showing low figures or something was wrong with my fuel delivery anyway?
Since then my WUR packed up (which could have been the cause of the leanness) and sent it off to be rebuilt and adjusted to flow more fuel at WOT, which never worked properly and every time I stopped the car and started it again it would splutter for the first minute or so, eventually it went back up to 9m who put a 965 WUR on there and the seventh injector, new fuel pumps and a new distributor (the control arm had rusted through), then the ignition was set at 29 degrees and spent a long time on the rolling road adjusting everything and dialling in the seventh injector, it ran fine albeit I couldn't feel any difference between what it was like at 32 degrees and 29 degrees with the extra fuel.
Don if you use the attached charts below from last year as being almost what you advise me to do now, i.e.: drop the seventh injector what should I do from there? There are guys on here with way over 400bhp at the wheels with CIS and being conservative mine is around 350rwhp (if that dyno is correct of course)

BTW on my first post that shows the other 930 pulling 510fwbhp, he was running 0.85bar and CIS, I didn’t see his AFR chart, that must be some turbo!!

Here are last year’s charts

 

I am now showing just how un-educated i really am I have read the IT number at the bottom of the dyno graph above as what the ignition timing was, i've just realised that it's Inlet Temp. Ok so i have no idea what the timing was set at last year, i do however know that it's at 29 advance now (only cos i'm reading that off the 9m chart)

Sorry

A better shot of the 9m chart is here although it doesn't show the AFR, I've finally sussed out how to convert PDF to JPEG

 

I really love the MAP sensor functionality on my Electromotive XDi! Granted I'm still on CIS, but as the the RPMs come up and the boost builds the sesor is quickly cutting back my timing! I regulary check the timing with a digital multi-meter connected to the ignition module. Driving around town with no boost (cruising), my timing is at about 23 -24 degrees. On a WOT third gear run, it quickly drops to 18 degrees. Granted this is twin-plug ignition.

I plan to connect a permanent Innovate AFR gauge where the clock currently is, just as soon as I get some extra "mods" money. Right now, I'm using an Innovate LM1 and I suspect that with my Imagine Auto fuel head that I could cut back a little bit more on the fueling. I too, think I might be a tad rich. I plan to check it this weekend.

 

I tuned it with 91 octane from a corner Citgo station, and run it on Chevron or Amoco 91 octane.

I used a an EGT probe for each side's exhaust temps (about 3 in from the port), and I used a knock sensor to see any problems. In addition, we read the plugs after every other run - a loop with a light.

My exhaust temps were 1570 at 6000 rpm, 13.1:1 at 15 degrees of timing. And no knocks. Max temps we were going to tolerate were 1650.

Sandman - I set my cruise timing at 24, same as you with, with AFR's of 14. My EGT showed over 1600. I advanced the timing to 36 and the temps dropped to approx 1400, same AFR. FYI...

On a modified engine, I beleive it will take what it wants. With out a dyno (that loads the motor), AFR meter and EGT meter, you are just guessing on a modified, air cooled turbo motor.

One last example, from my engine. At idle, my AFR is 11.2. If I try to set it to 14 or so (as suggested on a much earlier post), it will not run. In addition, it likes 22 degrees of timing at idle, not anything close to stock (-2 if I remember).

I really thought I was gonna get flamed from my earlier post, talkin all that heresy about AFR's.

 

You da man. Alot braver than I am.

 

A question I forgot to answer, I have no idea what plugs are in the car, which ones would you advise? I think I’ll get a local specialist to change the plugs and a basic service and get it back on the rollers and take a fresh look at the AFR, what's baffling me is that last year with the standard WUR and no extra fuelling the AFR was quite level, albeit lean at the top end, the chart from yesterday is erratic, maybe the plugs are all knackered and just not burning the fuel? I'm ready to trade it against a 996 GT2

 

Ah yes...plugs! I think that's the current "weak link" in my engine! I'm running the "El Cheapo" NGKs. When you've got 12 of the folkers...it adds up quickly! I'm thinking about running something from Denso or possibly the original W3DPO (or whatever it is...R2D2 or C3PO)...

 

Don,

Are you running 91 just around town and an occasional romp on the boost? What about the track? Do you run 91 or 100 there?

 

sand_man,
Nothing wrong with the NGK's. I run the NGK Copper's on my twin-plug, Never had a problem with fouling except maybe during cold startup. I may get flamed, but I would avoid the Bosch Platinums. I tried a set after converting to twin plug. They had a very short life.....center electrode wore out too soon, IMHO.

 

Both - I dial down the boost for track - .8 bar. I rarely see WOT around town or even out in the boonies where I live. That's why I wanted good low end and designed for it - high CR, advanced timed cams, stroked crank, EFI.

Next year tho, I'm gonna buy some EVO cams and see how that goes.