Guys - piggybacking on this thread - hope you don’t mind.

Car is a ‘91 964T. 3rd gear at redline (full boost 1.0 Bar) my AFR is 11.0 and the adjustment on the WUR is maxed out - the piston on the back is pushed in as far as possible - as far as I can tell. Not sure if altitude makes a difference - and the 964T WUR has altitude compensation - but just in case - I’m in Denver at 5200 ft.

Anything else I can do to get to the coveted 12.0 AFR at redline?

TIA for any insight.

I'm still learning about this too. But maybe if you post your Cold & Warm pressures some of the more experienced fellas will have some advice.

Minor Update - took the car for another drive on the weekend and when I got home I loosened my air filter and adjusted my AFR to 14.7 ish at idle from around 15.5, and then had to lower my idle back down to 900 RPM. The idle mixture screw was as described, push down and turn to lean or enrichen the mixture. I was able to peer thru my rear window and watch my Innovate Technologies gauge as I made the adjustment. Took a little effort to turn, more than I expected but probably better to be stiff adjustment since not alot is needed. So I think i'm all good in that regard.

Will also try to raise my enrichment pressure by.1 bar and see if it helps the mid range at all.

Idle AFR should be 13.0-13.5, cruise should be 14.5-14.8 (target). If idle is at 14.7 cruise will likely be too lean. Each engine has a sweet spot for idle AFR, I tune to that sweet spot and let cruise fall where it falls as this isn't my long distance vacation car so better running engine trumps optimal fuel mileage.

If rpm went up, it wanted the extra fuel - I do as Brian does. Do not get stuck on idle AFR number - give it what fuel it needs. Mine is around 12.5. It may be happier with more idle fuel than present.
You won't help mid range AFR much by increasing WP by 0.1 bar.
Alan

OK thanks guys, I didn't know what my idle AFR should be so I put it at 14.7ish. I'll maybe play with it some more soon and see if it makes any improvements.

Perhaps i'll leave my enrichment pressure as is until after my dyno session this Friday. Will be nice to have a graph of my AFR's.

I also noticed 2 spark plug wires had been touching and arching (white discolored area on red Clewitt wires), I wonder if that's contributing to mid range sluggishness. It seems like if I go hard thru the gears it gets up and goes great, but if I go hard into throttle in 3rd gear from a 40-50 mph roll, it doesn't want to go as well.

Jumping in here because I hope to be working on this tonight or tomorrow.
I have a new Leask WUR that was set by him based on my modification list. I had the improved diaphragm installed and have the RPM delay.
Reading this thread and Brian's statement below I am assuming that I should just get the car running and up to temp.

First: I need to check the idle AFR and adjust if needed.
Second: If I have a rich or lean condition adjust the WUR pressures.
Third: Once AFR's are good through the range and on boost then set the delay RPM based on the AFR readings at boost or when boost comes on?? Not sure here because the OP is not running a RPM delay.
I have Brian Leask's instructions but it's good to get all opinions from those that have done it.

Hi Derrick, yes I think you've got that order correct.

1 - Set idle AFR - @ approx 13-13.5 as per Brian, adjust idle speed after if needed (big flat screw driver on the side of the throttle body). This can be tricky settig the Idle AFR mixture, i'm lucky that my arm is skinny enough to fit between the my custom intercooler and underside of the engine compartment and I can look thru the rear window and watch my AFR gauge change as the car is running. I read to rev the engine after making an idle AFR adjustment, whether it makes a difference or not, i don't know, but I did it.

1 - Check cold pressure, warm pressure & enrichment pressure to verify what you've got. Brian sent me specs of what my WUR was set to when I bought mine about 2 years ago, but this month I found my actual WUR pressures did not match what he sent printed on the written spec sheet. I'm certainly not saying Brian set the WUR wrong or the mis-recorded the specs he provided, but for some reason they didn't match, no biggie, I reset them and i'm glad to have learned something new about working my car.

Use or borrow a trickle charger for this. My car is fairly modified and probably easier than stock cars to do these modifications, but it still is a good 1/2 hr of fuel pumps running after getting intercooler off and CIS pressure gauges hooked up and battery on a charger and waiting for WUR to warm up then trying to make changes to pressures. I have a VOLT meter in my cigarette lighter and could see it draining the battery.

2 - yes adjust as needed, hopefully you'll be close already. Raise pressures to lean it out, lower pressures to enrichen them.

3 - RPM switch, sounds like an easy thing to play with once installed. Change RPM chips as needed. I'm not sure if you'd go to a higher RPM chip to correct a rich AFR or vice versa. But it should be pretty obvious after 1 or 2 changes & drives.

Minor update, I bumped my enrichment threshold up .1 and went out for a rip. It seems like the lowest the AFR dips is low 11 then back up to 12-12.5 out to redline. Seems to pull best as is. I don't think I'll make any more adjustments to my WUR unless the dyno shows anything that looks off tomorrow.

Thanks everyone for all the great information in this thread. Really a great primer on the process to setup a welltuned CIS car.

Alan if you're around can you have a look at my Dyno thread and see my AFRs on the dyno. Let me know your thoughts if you'd leave all as is or make more changes.

Thanks.

AFR check after new turbo
 

Ok I’m too lean upper 13- low 14 AFR

When I first crack the throttle or rev the engine it goes lean to 14.5 for a couple seconds. Is this normal or something I can adjust?

Cold 1.9. Not totally cold. 80 degrees out and drove it about an hour before. So Brian’s setting of 1.7 is probably correct.

Warm 3.55 lower than the 3.65 on the paper

1.0 bar boost 2.6. Slightly higher than the 2.5 on Brian’s paper.

When I closed the valve the pressure went to about 90psi or 6 bar. Not 100 psi.
Turned the pumps off and it dropped to 2.2 bar and did not hold for more than 30 min. Started to bleed off.
Bad check valve?

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I did have a look, just not a lot of internet where I am right now.
Ideally the top end would be lower AFR. Maybe tuning it won't give any more - you may be at the limit. In which case dropping WP will only make your mid range worse, and ideally it would/should be smidgeon higher.
How often do you plan at running at 6000 rpm? I would def not run any more boost tho and as I think spuggy? noted - he has run like that for some time. Your only other option is to try dropping WP by about 0.3-0.5 bar to get the 6000 rpm AFR down to safer limit, and put up with the lower AFR in the 4500-6000 range (assuming you fit a leask sw to deal with the rpm below 4500)
Alan

Thanks Alan, At the track I wind it up to 6800 ish often. Maybe I should change the enrichment threshold which sounds like a similar thing to the Leask switch. There are 3 screws on the back of my WUR that I can turn to change this. Maybe I'll experiment with that.

Derrick, my enrichment pressure was also set very low like around 2.7, so I moved it up to be within .5 bar less than my Warm Pressure and that made a huge difference to my car. Brought AFRs very close to where they should be. My neighbour rigged me up a fitting for my air compressor that had a 15 lb adjustable pressure gauge. Made it a lot easier to fine tune my pressure to simulate 13 lbs boost for the enrichment setting.

Chris,
I lowered my warm pressure to 3.4bar from 3.55bar to try and get the AFR's in the 11's and out of the high 13's. I will reassemble tonight and see where I'm at. Now that I'm in there I understand the process better. I have to lower my boost and get the AFR's safe before messing with the on-boost pressure and RPM delay. My WG's came with springs that are too large for my application.

I'll post the pressure changes, RPM solenoid changes and results to hopefully help other new guys like us in the future.

Any idea how to get more fuel at part throttle and up to 4000? I have the rpm solenoid set at 4K and I’m still too lean (14afr)from off idle to fuel dump. Then it goes to 11.2. Idle is still good at 13 AFR.
But I have another issue (misfire) over 4K I need to figure out. But that’s another thread.


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^^^

Deez, maybe I'm not reading you right, butt why do you consider "off idle/part throttle up to 4K in the 14s" as too lean? I'm assuming that is not boosted running (WUR's WFO/boost enrichment not a factor), but cruising and/or steady, gradual, slow throttle?

By comparison, I'm almost always in the high 14s during partial throttle, non-boost running, and consider that just about perfect.

Also, are you taking the AFR readings while motoring down the road (under load) or while opening the throttle at a stand still (an earlier post or two of yours makes it seem like you are talking about throttling it at a stand still, but maybe I'm not understanding you correctly)? If you're looking at the AFRs in a no-load situation, they are pretty meaningless (except for idle, buttofcourse).

^^^ I’m not that inept. While driving. 13 at idle and high 13 low 14 at cruising. If 14’s are good then I’m ok. I need to figure out my other issue and then set the boost dump pressure.


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^^^

Theoretic perfect AFR for cruising is 14.7 (stoichiometric ratio), so you are actually on the rich side and sending a bit more than necessary unburnt fuel out of the tailpipe. I say "theoretic" as not all engines are going to run smoothly at that AFR - mine does and my steady highway cruising is even a few tenths higher depending on weather conditions, etc.

I run over 15 at light cruise. Did that also when CIS but with the help of AIC-1 to control fuel. I have two AIC units available if any of you with fueling problems like to wrench/tinker a bit but then get enough fuel on top rpms too. For me dialing the AIC-1 to almost perfect was very easy.

Just want to add 14.7 was a target back in the days when we had real gasoline with no ethanol mixed in. I don't know what kind of gas you're using but if it's E10 gas with around 10% ethanol mixed in the target will be somewhere around 14.1
That's because the ethanol molecule has oxygen in it so you have to run a little richer AFR to make up for that or it will run a little lean.

When I had a good running '87 911 turbo with idle speed timing around 10 degrees before TDC, 964 cams set at 1.25mm intake valve lift at TDC before the intake stroke, and a CIS flowtech 007 fuel head it ran best with idle AFR around 12.8:1 and 65mph steady speed cruise AFR on flat roads was around 15:1
CIS without a frequency valve controlled by an O2 sensor in the exhaust header is never perfectly consistant all the time and never will be but it can run very well within it's limits when everything is set up right

In the end maybe it's best to forget about all the numbers and just set it by ear where it runs best. That said not everybody can do that but if you have experience adjusting carburetors by ear you may be able to do that with CIS if it's not too far off.

And to back up what Jim is saying, I found that when my cruise AFR was a bit too lean, I could feel surging while driving at a constant speed. Slightly richening WCP from there got me to about 14 as my cruise AFR where my car is happy.

Best power is at around 100 deg f rich of peak egt, best econ around 35-50 deg lean of peak egt. You may need to be even richer than that to provide additional protection esp under boost or running long periods at high power.

modern cars in steady state cruise are at the ragged edge of lean misfire, but that's because we can do that with a modern ecu with sequential ignition and injection.

stoich is neither best power nor best economy.

You need to factor in all that TexAZZ humidity helping slow the burn rate and reducing the chance of detonation.

Good info Jim F. (different than "Effff Jim!" :D) and FlyingFlamer!


Deez, I'm reminded of the TexASS humidity each time I stop the car and so much water is pouring out of the evap box that it looks like there's a radiator leak. Hmmmmm, maybe that could be a ready source for water injection (just need to use some of the meth from my pipe to mix with it!!!).

Lol I tried to insert a super excellent graph that I have that shows the relationship between AFR, EGT, CHT, power, and specific fuel consumption. Actually on this plot it's FAR nor AFR so its inverted, but still clear to see the relationship. I guess it didn't work.

I'm at 34,000 heading to TEXASSS as I type this (Allen/Dallas for a couple of days), so I'll try and re link it later.

Question about the cold pressure. It wasn't mentioned in the thread.
My warm idle is good but when moving the car last night I noticed the car was drowning during warm up 9.8 - 10.1 when first started. I could hear it was too rich. So I'm going to raise the cold pressure a little tonight.

What should the AFR be during warm up? I would think 13.0 but thought I would ask.

And about how much BAR pressure would raise it 2 AFR points?

Every car is a bit different, but mine likes around 12 at cold start, maybe a hair less, which then slowly rises as the WUR warms up. I actually have to tweak mine again since it seems to be starting at around 13-13.3, which it just doesn't like. PITA, since each adjustment seems to have a slight effect on the other adjustments, so after richening ccp, my wcp will probably be a bit richer too and require adjustment.

My Cold pressure is set at 1.4 bar, it starts and idles nice so i'm not messing with it, I can't recall what my cold AFR is, probably 13-14ish.

I think the Cold pressure adjustment is one of the easier ones to make so may be worth tinkering with.

Minor update - just flogged my car at Mosport and the AFR gauge shows me dipping into mid 11's and back up into 12's before redline. I ran my best laps ever and the car was great. It's a hot day too. Oil Temperature never going above 190. I don't think I'll bother making any further adjustments.

I suppose if I were to adjust anything maybe it would be the enrichment threshold but I'm not sure what that'll really gain me? Other than changing the point at which the AFR start heading towards lean. I'm not sure if raising the enrichment threshold would lower the point at which the AFRs start leaning out, allowing me to have 6500+ rpm going into 13's from current mid 12's. Any comments?

I don't believe changing the enrichment threshold will have any effect on the AFR at higher RPM
All the threshold adjustment does is determine the RPM at which the boost dump will take place, and then it stays that way until the rpms drop from letting off the gas. So you should get the exact same amount of fuel at 6500rpm whether the threshold is at 4200 or 4800 rpm, for instance. Going higher with the threshold is only necessary if the AFR dips too low at the point of enrichment. The thinking is that at higher rpm, it is using more fuel, so it will be leaner than it would be at a lower rpm. Just be sure that you aren't going too lean just prior to enrichment if you raise it. Each car has its sweet spot for when to enrich and the datalogging either while driving or dyno tuning really helps to figure that out.

I never felt much performance change when I fiddled with those 3 Brian Leask threshhold adjustment screws he puts in the bottom of the WUR.

If you take the thing apart you can see that the largest diameter spring seats against those adjustment screws so screwing them in will compress that spring a little. If I remember correctly there's 2 or 3 springs in there of different diameters.

Try adjusting them. Can't hurt unless you screw them in too far and they fall inside or something.
Count how many turns you make so you can go bck to where they were if you want.

I’m good at idle and cruising. I even leaned it out more at cruising so the AFRs are mid to upper 14’s. The disc is all the way in and I have a 4800 rpm pill and I can’t get out of the 11’s on boost.
Any suggestions?
I feel like moving the disc in changed nothing. Could something be stuck inside the WUR?


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I think it's strange your disk is pushed so far in. Mine is probably 1/8" in at most. I wonder why yours is so far off?

When I had one the disc wasn't in all the way either.
I think some people go too far with one WUR control pressure adjustment and because they don't know what they're doing they try to compensate for that by adjusting the CO adjustment too far one way or the other.
Then CIS can become a miserable frustrating mess that never runs right all the time.
and...
EFI becomes much more attractive if you can afford it.