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

Turboflash

Turboflash

TY 4 Stroke God
Joined
Mar 18, 2019
Messages
2,442
Location
Southern MN
Country
USA
Snowmobile
'17 ZR9000 Ltd. 137 - PEFI Stage 4
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!!
 

Around 46 pounds should put you in the ballpark. Then test and bring it down accordingly.
 
Last edited:
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!!
Click to expand...

WOW is that full throttle A/F ratio? Thats obviously way too lean. Have you checked the fuel pressure at that 43.5 lbs key on or just assume its 43.5 lbs key on?

I had a regulator here that only would run at 39 lbs key on is why I asked. It typically ran low 12.2-12.3 and upping the fuel pressure to 44 lbs got it back to where it should be in the mid 11's, this was prior to closed loop, so it took 5 lbs fuel pressure to get it there. I put the regulator in a press with a socket on the bottom and a small socket on the top of the regulator and pressed it in tighter to tighten the internal spring. I checked it with an air hose and regulator to set it properly off the sled.

Maybe you are running and adjustable regulator however. You will need to up it quite a bit to get that high 13 and 14 under control. Some thing doesn't see right with it that lean however. Thats another engine burn down waiting to happen! Does it have a big fuel pump in it? Maybe the fuel pump is taking a dump?

Not to rub it in, but boy do I ever like the Hurricane GAP data logging option after seeing this. You don't have to be looking at that A/F gauge all the time and wondering the health of the fuel and engine systems.
 
If thats full throttle afr your gonna need quite a bit of psi to lower that. Like knapp said, I wonder if the pump is getting weak or the socks in tank are real dirty? Maybe a vacuum problem with the regulator itself or the line to it and the rate isnt rising accordingly to match the boost so fuel psi is down when under boost?
 
KnappAttack said:
WOW is that full throttle A/F ratio? Thats obviously way too lean. Have you checked the fuel pressure at that 43.5 lbs key on or just assume its 43.5 lbs key on?

I had a regulator here that only would run at 39 lbs key on is why I asked. It typically ran low 12.2-12.3 and upping the fuel pressure to 44 lbs got it back to where it should be in the mid 11's, this was prior to closed loop, so it took 5 lbs fuel pressure to get it there. I put the regulator in a press with a socket on the bottom and a small socket on the top of the regulator and pressed it in tighter to tighten the internal spring. I checked it with an air hose and regulator to set it properly off the sled.

Maybe you are running and adjustable regulator however. You will need to up it quite a bit to get that high 13 and 14 under control. Some thing doesn't see right with it that lean however. Thats another engine burn down waiting to happen! Does it have a big fuel pump in it? Maybe the fuel pump is taking a dump?

Not to rub it in, but boy do I ever like the Hurricane GAP data logging option after seeing this. You don't have to be looking at that A/F gauge all the time and wondering the health of the fuel and engine systems.
Click to expand...
KA - That's why I posted. WAY TOO LEAN! Engine is brand new. I told the guy he cannot run it until we get AFR into the high 11's. It will deto and toast. He's running 96 octane (mix of Sunoco 110 with 92 ethanol pump gas). I told him it will still wreck his engine and ECU will always be reducing timing trying tp prevent deto). He thinks his 96 octane fixes it and told him no.
Yes, 43.5 psi key on engine not running. Checked with a high quality automotive style fuel injection kit (SnapOn). Fuel pressure does rise with pressure on signal line to regulator.
Sled has that high-buck PEFI Fuel Pump upgrade on it with a nice Radium regulator (non-adjustable). (https://precisionefi.com/collections/9000-series/products/fuel-upgrade-kit).
1641179538243.png

I can richen up easily by starting to restrict return line. Return line is 3/8" diameter. I think pump is a 255 lph.
Cold idle is 12.8-13.2. Hot idle is 14.2-14.4. By restricting return line I can easily get AFR to 10:1 and engine loads up (of course).
This PEFI Stage 3 tune is supposedly 280HP with THEIR PM. Well, this sled has a D&D Tech2 Stainless PM which if we go back and read through muffler threads is probably the highest flowing 2.5" PM you can find. A few guys commented on how restrictive the PEFI PM is compared to orther 2.5" PMs from TD or Hurricane. In fact, one guy said the D&D Tech2 on this tune is almost 20HP more than with PEFI muffler (on dyno). So the PEFI muffler is a derby chip.
He doesn't want to de-tune sled by getting a more restrictive muffler. So, I hope if we get an adjustable fuel pressure regulator, we can keep increasing fuel pressure until we get high 11 AFR. I posted because I was curious is anyone has already been down this road.
AFR is high everywhere. AFR hot idle is 14.2-14.4. At light cruise (5500-6000 RPM) AFR is high 15 to even 16!!!! From that point, the AFR does richen as more throttle is applied but it's still way too lean. Best as could tell, it was about 13.8-14 at WOT.
So, if I give it 5-7 more pounds of fuel pressure, will AFR drop to mid 11's? That's the question. And, if I do that, what will happen at idle? Will it be too rich or will idle AFR just be down to low 11's or something? Don't want to foul plugs at idle.
The system seems to be working fine. I even had his fuel injectors cleaned professionally so I know they are 100%.
I think the D&D Tech2 Stainless PM is just that less restrictive compared to PEFI PM. Of course, that Stage 3 PEFI map was built on the dyno with their 2.5" PM. I bet if we put a PEFI muffler on this sled, it would be fixed because the entire system would be exactly what they built on their dyno.
 
Turboflash said:
KA - That's why I posted. WAY TOO LEAN! Engine is brand new. I told the guy he cannot run it until we get AFR into the high 11's. It will deto and toast. He's running 96 octane (mix of Sunoco 110 with 92 ethanol pump gas). I told him it will still wreck his engine and ECU will always be reducing timing trying tp prevent deto). He thinks his 96 octane fixes it and told him no.
Yes, 43.5 psi key on engine not running. Checked with a high quality automotive style fuel injection kit (SnapOn). Fuel pressure does rise with pressure on signal line to regulator.
Sled has that high-buck PEFI Fuel Pump upgrade on it with a nice Radium regulator (non-adjustable). (https://precisionefi.com/collections/9000-series/products/fuel-upgrade-kit).
View attachment 164884
I can richen up easily by starting to restrict return line. Return line is 3/8" diameter. I think pump is a 255 lph.
Cold idle is 12.8-13.2. Hot idle is 14.2-14.4. By restricting return line I can easily get AFR to 10:1 and engine loads up (of course).
This PEFI Stage 3 tune is supposedly 280HP with THEIR PM. Well, this sled has a D&D Tech2 Stainless PM which if we go back and read through muffler threads is probably the highest flowing 2.5" PM you can find. A few guys commented on how restrictive the PEFI PM is compared to orther 2.5" PMs from TD or Hurricane. In fact, one guy said the D&D Tech2 on this tune is almost 20HP more than with PEFI muffler (on dyno). So the PEFI muffler is a derby chip.
He doesn't want to de-tune sled by getting a more restrictive muffler. So, I hope if we get an adjustable fuel pressure regulator, we can keep increasing fuel pressure until we get high 11 AFR. I posted because I was curious is anyone has already been down this road.
AFR is high everywhere. AFR hot idle is 14.2-14.4. At light cruise (5500-6000 RPM) AFR is high 15 to even 16!!!! From that point, the AFR does richen as more throttle is applied but it's still way too lean. Best as could tell, it was about 13.8-14 at WOT.
So, if I give it 5-7 more pounds of fuel pressure, will AFR drop to mid 11's? That's the question. And, if I do that, what will happen at idle? Will it be too rich or will idle AFR just be down to low 11's or something? Don't want to foul plugs at idle.
The system seems to be working fine. I even had his fuel injectors cleaned professionally so I know they are 100%.
I think the D&D Tech2 Stainless PM is just that less restrictive compared to PEFI PM. Of course, that Stage 3 PEFI map was built on the dyno with their 2.5" PM. I bet if we put a PEFI muffler on this sled, it would be fixed because the entire system would be exactly what they built on their dyno.
Click to expand...

Something really wrong there if its that lean everywhere. I'd try refreshing the tune or replacing that fuel pump or supply system. It's not the muffler making it that lean. I'd put a fuel pressure gauge where you can see it and make a run.

Perhaps it need to go to ProLines track dyno to make some runs while logging the fuel pressure and are sure it holds under a hard load?

Just because its 43.5 lbs key on does not mean the pump will keep up under a hard load WFO run. 5-7 added psi fuel pressure will get you about 1 maybe 1.5 points best on the A/F. Its not going to be enough. I suspect the tune didn't import properly if its that far off even at idle and midrange.

I just wonder if you got a tune on there setup for their higher pressure fuel system like the stage4? This would make the most sense, because your a long way from having enough fuel pressure there. I'd guess your 10 lbs away from the proper fuel pressure perhaps? Isn't their stage 4 setup set for the bigger regulator that's runs about 10 more PSI too?

If nothing else I suppose an adjustable regulator setup at about 54 lbs key on high do the trick, but if that pump is 255 will it keep up? I believe Hurricane runs about a 340LPH big pump setup.
 
Ya no way the muffler is leaning it that much. Im the one who shared the dyno of the pefi muffler and dd tech 2 on my buddies sled and the previous owner switched mufflers all the time depending if he was racing or trail riding. Afrs were fine with either but it wasa 3R map and not the regular stage 3. The dd tech 2 flows well for 2.5 but doesnt outflow a 3” muffler and I can swap from pefi muffler, td 2.5” and viney fab 3” and while I do have closed loop my fuel multiplier isnt making drastic swings to keep things in line. Im gonna agree with knapp that their is an issue in the tuning or fuel system.
 
Any chance you ran this sled with a different muffler without touching anything else? Same day ? Want to here numbers if you did or do
 
Had pefi tune bundle installed march of 2019 by speedwrks on my 2018 t cat, nothing but trouble with it, constant trouble codes, would only run decent on level 2. Was talking with alan ulmer about it...he had me send him my ecu to check it out,seems mine was any early flash with many revisions since, he reflashed with most current version, no problems since...food for thought!!
 
1nc 2000 said:
Check voltage drop to pump?
Put a heavy duty relay harness direct from battery to pump.
Not enough electrical power will cause this also.
Click to expand...
Thanks. Sled has that Boost Kinetics EXTERNAL FUEL PUMP HARNESS RELAY on it with new battery. Battery load tests really good. Voltage 13.3 engine not running. Engine running 14.5. That should be good.
The radium regulator checks good to boost reference. As we increase pressure on signal hose, fuel pressure increases same so regulator appears to be working correctly. Just need higher pressure to deliver more fuel. Waiting for TD adjustable regulator kit. Should see it by Wednesday and will test by Thurs/Fri. Plan on turning it up to 48 and see how much AFR comes down. Maybe need closer to 50? We'll see.
 
Turboflash said:
Thanks. Sled has that Boost Kinetics EXTERNAL FUEL PUMP HARNESS RELAY on it with new battery. Battery load tests really good. Voltage 13.3 engine not running. Engine running 14.5. That should be good.
The radium regulator checks good to boost reference. As we increase pressure on signal hose, fuel pressure increases same so regulator appears to be working correctly. Just need higher pressure to deliver more fuel. Waiting for TD adjustable regulator kit. Should see it by Wednesday and will test by Thurs/Fri. Plan on turning it up to 48 and see how much AFR comes down. Maybe need closer to 50? We'll see.
Click to expand...
Certainly not a bad idea to try another regulator at this point. But if you need 50psi on any of the pump gas tunes out there likely something else wrong. Wondering if your fuel pressure is actually low or your AFR reading is wrong. Has your deto light come on at all under acceleration?
 
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