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AFR too high; how much more fuel pressure is needed?

No deto light under accel. Only flashes deto light within miliseconds of letting off throttle.
Deto light occassionally flashes at 5500 - 6200 RPM cruise. If I whack to WOT from 6000, no deto light but when letting off, deto light flickers.
If I restrict return line manually, AFR comes down (even to 10:1). Tells me fuel is too low. Just add more flow, and AFR will be fine in low to mid 11's.
 

Turboflash said:
No deto light under accel. Only flashes deto light within miliseconds of letting off throttle.
Deto light occassionally flashes at 5500 - 6200 RPM cruise. If I whack to WOT from 6000, no deto light but when letting off, deto light flickers.
If I restrict return line manually, AFR comes down (even to 10:1). Tells me fuel is too low. Just add more flow, and AFR will be fine in low to mid 11's.
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I gotta ask!!
What the hell is pefi doing to help you out TB
With a brand new motor shoulded the tuner be involved and offering some help with the tune they designed?..especially being so lean..
 
yamamarc said:
I gotta ask!!
What the hell is pefi doing to help you out TB
With a brand new motor shoulded the tuner be involved and offering some help with the tune they designed?..especially being so lean..
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Thats a damn good question. Wonder what else is going on in that tune. Speedwerx had the stage 3 280 tune listed as a 91 octane tune beginning of last winter. Its now listed as 91/110 mix tune. I think they are taking some necessary precautions on a questionable setup imo. They do not even sell the stage 4 kit at all. I think its time for PEFI to revist the 998 tuning and get some free updates out to all their customers.
 
justinator said:
Thats a damn good question. Wonder what else is going on in that tune. Speedwerx had the stage 3 280 tune listed as a 91 octane tune beginning of last winter. Its now listed as 91/110 mix tune. I think they are taking some necessary precautions on a questionable setup imo. They do not even sell the stage 4 kit at all. I think its time for PEFI to revist the 998 tuning and get some free updates out to all their customers.
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When allen updated mine this fall it was with revision #5 i believe he told me.
 
When I spoke with PEFI today, it was a very predictable conversation (I have some experience trying to talk to Sebastien Guay - owner PEFI).
1. They said if tune download was corrupt, the sled wouldn't even start. They said there is a ECU check after the download to make sure it is not corrupt.
2. The Stage 3 tune was developed on their dyno in late 2016 when 2017s were just coming out. It was developed using their 2.5" PM which is a baffled muffler. The muffler on the troubled sled is a D&D 2.5" Tech2 Stainless. It has NO baffles of any kind. It is literally straight through. It has a perforated 2.5" core with some kind of packing exterior to the core. You can literally look straight through muffler with no restriction. They told me this muffler may as well be a drag pipe as it provides almost no back-pressure at all.
3. They were able to find this sled on their system (by VIN) and determine it was licensed at Stage 3 in Dec. 2017.
4. As predicted, they told me to buy one of their 2.5" PM (which will detune this sled about 20 HP) to fix problem.
5. They said AFR on dyno with their muffler will be mid 11's at WOT.
6. They have not experimented with adjustable fuel pressure regulators so they could not provide any advice other than to say it could work.

We tested same sled later today with same muffler only with an exhaust outlet restriction cone spot welded in. I think the hole was about 1.85". AFR came down to high 11's and low 12's on same gas. Temps a bit warmer than previous. Could tell HP was down a bit by RPM. It would not pull as much clutch weight.
Conclusion:
1. ECU map is programmed for (restrictive) PEFI PM to mid 11 AFR (WOT). PEFI Stage 3 280HP.
2. This D&D Tech2 2.5" muffler has so little restriction and flows so high that AFR goes lean (on PEFI Stage 3 map). (Also pretty loud!)
3. Sled owner either has to install more restrictive muffler OR add fuel to get AFR in line.

P.S. Adjustable fuel pressure regulator was ordered and expected within next few days. Plan is to dial up fuel pressure to about 48-50 lbs and re-test. Will post findings. I guess this muffler does make a substantial difference compared to PEFI PM.
 
Turboflash said:
When I spoke with PEFI today, it was a very predictable conversation (I have some experience trying to talk to Sebastien Guay - owner PEFI).
1. They said if tune download was corrupt, the sled wouldn't even start. They said there is a ECU check after the download to make sure it is not corrupt.
2. The Stage 3 tune was developed on their dyno in late 2016 when 2017s were just coming out. It was developed using their 2.5" PM which is a baffled muffler. The muffler on the troubled sled is a D&D 2.5" Tech2 Stainless. It has NO baffles of any kind. It is literally straight through. It has a perforated 2.5" core with some kind of packing exterior to the core. You can literally look straight through muffler with no restriction. They told me this muffler may as well be a drag pipe as it provides almost no back-pressure at all.
3. They were able to find this sled on their system (by VIN) and determine it was licensed at Stage 3 in Dec. 2017.
4. As predicted, they told me to buy one of their 2.5" PM (which will detune this sled about 20 HP) to fix problem.
5. They said AFR on dyno with their muffler will be mid 11's at WOT.
6. They have not experimented with adjustable fuel pressure regulators so they could not provide any advice other than to say it could work.

We tested same sled later today with same muffler only with an exhaust outlet restriction cone spot welded in. I think the hole was about 1.85". AFR came down to high 11's and low 12's on same gas. Temps a bit warmer than previous. Could tell HP was down a bit by RPM. It would not pull as much clutch weight.
Conclusion:
1. ECU map is programmed for (restrictive) PEFI PM to mid 11 AFR (WOT). PEFI Stage 3 280HP.
2. This D&D Tech2 2.5" muffler has so little restriction and flows so high that AFR goes lean (on PEFI Stage 3 map). (Also pretty loud!)
3. Sled owner either has to install more restrictive muffler OR add fuel to get AFR in line.

P.S. Adjustable fuel pressure regulator was ordered and expected within next few days. Plan is to dial up fuel pressure to about 48-50 lbs and re-test. Will post findings. I guess this muffler does make a substantial difference compared to PEFI PM.
Click to expand...

Turboflash said:
When I spoke with PEFI today, it was a very predictable conversation (I have some experience trying to talk to Sebastien Guay - owner PEFI).
1. They said if tune download was corrupt, the sled wouldn't even start. They said there is a ECU check after the download to make sure it is not corrupt.
2. The Stage 3 tune was developed on their dyno in late 2016 when 2017s were just coming out. It was developed using their 2.5" PM which is a baffled muffler. The muffler on the troubled sled is a D&D 2.5" Tech2 Stainless. It has NO baffles of any kind. It is literally straight through. It has a perforated 2.5" core with some kind of packing exterior to the core. You can literally look straight through muffler with no restriction. They told me this muffler may as well be a drag pipe as it provides almost no back-pressure at all.
3. They were able to find this sled on their system (by VIN) and determine it was licensed at Stage 3 in Dec. 2017.
4. As predicted, they told me to buy one of their 2.5" PM (which will detune this sled about 20 HP) to fix problem.
5. They said AFR on dyno with their muffler will be mid 11's at WOT.
6. They have not experimented with adjustable fuel pressure regulators so they could not provide any advice other than to say it could work.

We tested same sled later today with same muffler only with an exhaust outlet restriction cone spot welded in. I think the hole was about 1.85". AFR came down to high 11's and low 12's on same gas. Temps a bit warmer than previous. Could tell HP was down a bit by RPM. It would not pull as much clutch weight.
Conclusion:
1. ECU map is programmed for (restrictive) PEFI PM to mid 11 AFR (WOT). PEFI Stage 3 280HP.
2. This D&D Tech2 2.5" muffler has so little restriction and flows so high that AFR goes lean (on PEFI Stage 3 map). (Also pretty loud!)
3. Sled owner either has to install more restrictive muffler OR add fuel to get AFR in line.

P.S. Adjustable fuel pressure regulator was ordered and expected within next few days. Plan is to dial up fuel pressure to about 48-50 lbs and re-test. Will post findings. I guess this muffler does make a substantial difference compared to PEFI PM.
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I know this has been brought up, but with PEFI response, and the chance of another expensive rebuild if something goes wrong, why not just bite the bullet and switch tunes. Sounds like you're already throwing money at it as a bandaid with the fpr. I'm sure there's a TD/Hurricane tune that will work with the existing hardware. Just my $.02 because I know I'd be worried about it every time I pulled the trigger.
 
That muffler is crazy flow. Anyone running that better be careful and or beware. Not surprised as DD has always brought great product over the years.
 
jonlafon1 said:
That muffler is crazy flow. Anyone running that better be careful and or beware. Not surprised as DD has always brought great product ov
jonlafon1 said:
That muffler is crazy flow. Anyone running that better be careful and or beware. Not surprised as DD has always brought great product over the years.
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I think it's more the precision muffler doesn't flow worth a crap.
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How are these PEFI tunes running around with 3" straight thru mufflers then? My bud has a 3" Sandale on his. Ulmer sets them up with 3" mufflers, or at least did. How does Hurricane and TD get by with all these big mufflers without going that lean?
 
KnappAttack said:
How are these PEFI tunes running around with 3" straight thru mufflers then? My bud has a 3" Sandale on his. Ulmer sets them up with 3" mufflers, or at least did. How does Hurricane and TD get by with all these big mufflers without going that lean?
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Knapp, I have three TD-tuned 998’s in the stable. Have tried many muffler and other combinations. TD gives you a muffler-specific tune. It’s always one of the variables they ask. When it gets to a certain level, they require you to install an upgraded fuel pump and adjustable fuel pressure regulator to get the tune. If you add a header, the tune parameters change again. My Winder is on the MS 17 tune, header, and 3” Super Quiet TD muffler. Per TD instruction, running 48 psi key on. Closed loop and data logging. AFR is perfect.

I don’t know if it’s pefi’s fault for not being as detailed and conscientious as TD, or if it’s the user’s fault for swapping in a muffler that pefi’s tune was never made to run. If I swapped a higher flowing muffler on my Winder, removed the fpr, leaned it out, and burned up the engine, that’s on me, not TD. Same might be said for the pefi customer wanting another 20hp and not using the right muffler...
 
snowcaine said:
Knapp, I have three TD-tuned 998’s in the stable. Have tried many muffler and other combinations. TD gives you a muffler-specific tune. It’s always one of the variables they ask. When it gets to a certain level, they require you to install an upgraded fuel pump and adjustable fuel pressure regulator to get the tune. If you add a header, the tune parameters change again. My Winder is on the MS 17 tune, header, and 3” Super Quiet TD muffler. Per TD instruction, running 48 psi key on. Closed loop and data logging. AFR is perfect.

I don’t know if it’s pefi’s fault for not being as detailed and conscientious as TD, or if it’s the user’s fault for swapping in a muffler that pefi’s tune was never made to run. If I swapped a higher flowing muffler on my Winder, removed the fpr, leaned it out, and burned up the engine, that’s on me, not TD. Same might be said for the pefi customer wanting another 20hp and not using the right muffler...
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Yes, I know how it works. Maybe what I should say is when we swap mufflers on the Hurricane tunes from say a 2.5" baffled trail muffler to a 3" straight thru muffler the A/F does not change much, maybe .2 is all, and of course closed loop will compensate for that now as well.

Being that far lean on the PEFI 280 is not normal, and lots of PEFI guys and their own dealers are putting different mufflers on them. Their trail muffler must be extremely restrictive with that much difference in A/F. I guess that's why they are burning so many of the PEFI's up because not many are running their branded muffler. They should specify this to the customer or at least make it known, possibly even include it with the tune package perhaps at least warn their users that they could blow their engine up should they not run their own brand of muffler.

At least warn the customer or dealers that is will be this EXTREMELY lean if not using their own muffler. Looks like my buds PEFI sled with the 3" on it is a ticking time bomb.
 
TD asks you what exhaust you are running but the tunes are not muffler specific. Same tune for 3" exhaust as 2.5". I asked them because I have the pefi muffler, td sq 2.5" and recently got a 3" viney fab. They recommend 48psi with key on with closed loop because that way the system is mostly pulling fuel rather than adding it and if the sensor or module fails you are safer if you happen to be running some wacky hardware. If you dont have adjustable regulator you are all still fine.The regulator was required for header before they had header specific tunes. Now that they have have header specific tunes you are only required to have big fuel pump for all header tunes.
Now regarding the pefi muffler which I have many miles of use on......It works good overall and yes its more restrictive then some of the straigh through mufflers but there isnt really a big seat of the pants difference. It didnt work as well as the td sq 2.5" muffler on a hurricane tune but that tune had no closed loop and was towards the end of the year so warmer weather and the afrs were a little towards the rich side, probably would of been better with closed loop. No issues running it on the TD sled as thats where it spent 2500 miles of its life, little less power than a straight through yes but doesnt make sled lethargic by any means. Like mentioned earlier, I am the one who shared the dyno results of my buddies 9000rr with stage 3r precision on the dyno comparing the pefi muffler and dd tech 2. I learned today that the previous owner(who is the one who had it dynoed) had it dynoed at D&D. Now I am a bit of a skeptic when someone is running their competitors product vs theirs on their dyno. No doubt the tech 2 flows more but was it as drastic as dyno showed.......I dont know. guys around here fab up straight pipes for lake race days with no issues. Ive swapped between 2.5 and 3" mufflers and viewed my data logs and fuel multiplier is doing very little different to keep afrs in check. Even without closed loop I would be safe to run. I dont understand how a tune can be so different that a muffler swap sends it right over into engine destruction territory. The tech 2 straight through muffler may flow more than some of the 3" baffled muffler but it certainly doesnt flow more than a 3" straight through muffler. All I can say with 100% certainty is that if it were me, after spending all that money on a rebuild, and now seeing this I would buy a gap map sensor and a tune from one of the 2 tuners utilizing gap and enjoy my much safer tuning and have the ability to play with hardware a little bit without having a meltdown and have fully functioning knock protection. You already have larger pump and exhaust so no new hardware required. From the past year or so I have concluded their is some sketchy schit going on in quebec.
 
Turboflash said:
Looking for input to correct high AFR on 18 TCat, PEFI Stage 3 280HP. Freshly rebuilt engine.
Sled is 18 TCat PEFI Stage 3.
PEFI fuel pump upgrade kit (returns to basket). Fuel pressure 43.5 psi key on engine not running.
Turbosmart BOV. Stock air box. D&D Tech2 2.5" PM.
95-96 octane gas (mix of Sunoco 110 w fresh 92 pump gas (w ethanol).
Testing this weekend with freshly installed AEM wide band kit. Ambient temps about 0F. AFRs way high pretty much all the time. Like high 13s and up even into high 14s! Way too lean!
How much more fuel pressure would be needed to AFR down into high 11s?
Thanks!!
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Have you tried a new 02 sensor they tend to show lean numbers when they go bad until they stop working at all.
 
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