Question about A/F ratios

Onefast99gsx · 10-07-2005

Can someone tell me if A/F ratio is not directly related to running lean or rich? Does it just indicate the content of the air & fuel that is there and not the amount of air & fuel? I would richen the piss out of it and dsmlink would show like 9:1 or i lean it and go around 11:1 but knock would never go away so that's why i'm asking my question. A/F must not tell if you are lean or not like an EGT would.

For months i've struggled with my car and knock in 3rd gear after around 5500 rpms. Last night while looking at something else I saw the vacuum hose going to the stock FPR was completely disconnected. It was also pinched by the firewall area. That's why i never picked up on it during the boost leak tests. Fixed it and took it out and was merely knock free after some hard 60-90 runs.

Thanks.

Outlaw1 · 10-07-2005

You are probably looking at Commanded A/F ratio. Your A/F ratio is exactly that, air/fuel mixture. No vacuum line to the fuel pressure regulator? Wow, lucky you didn't ventilate a piston.

You made 60-90 pulls in one night? ? ? That's a bunch of fuel! J/k.

Onefast99gsx · 10-07-2005

I spoke to Thomas of Dsmlink and he said the same thing. He said normally, it should have shown with the O2 readings but oddly it didn't so that's why he said to never go by O2 readings.

Yeah i made at least 8 or 9 60-90 runs last night. I know it sucks the fuel bad because i can see the difference on the 'ol gauge. You wouldn't believe how many pulls i did over the summer trying different stuff. I just never looked there to find it off like that. And even if it had been on, i probably wouldn't have caught the pinched line for who knows how long. The pinched line made it so it was never detected on a boost leak test. Any time i reached knock i always backed off it

Dam i'm happy. The car has so much potential at the track. I just have to take it there.

niterydr · 10-07-2005

glad you figured it out.
From June 25, 2005
......reasons for possible "knock"......
1) Failing FPR, inconsistent fuel pressure will cause
a great strain on injectors, and make the car
virtually impossible to tune. Injectors are rated on
a 43psi baseline, and are expected to rise in a 1 to 1
ratio. Any deviation will change in how the car is
tuned. By running a lower baseline pressure, you
'shrink' the size of the injector, and when the car
doesn't rise in a 1psi fuel pressure to 1psi boost
pressure, the car is near IMPOSSIBLE to tune
correctly.......

I remember writing that to you in an email. I didn't mention to check the vac line to it however. Are you going to the track on saturday now?

Onefast99gsx · 10-07-2005

Thanks...I remember you writing that to me as well as i have all those emails saved. It's really good that you save your emails to customers and even non-customers. Good for tracking purposes. I don't know when i would have found it. I was gonna take the head off over the winter thinking something was up with it so i would have found it then. A summer wasted though.

I was really giving it some serious thought. I have 5galls of 116 octane fuel that i want to use up this year. The only thing is that i don't want to wreck my 19" tires. I have my GSX 17" wheels. Three have 215/45 17's and one wheel has a 215/50 17" It's about 1" taller. I'm afraid to wreck my tranny or other drivetrain if i run it like that.

niterydr · 10-07-2005

Yeah, don't run at the track on mis-sized tires, its a good way to tear up drivetrain.

Onefast99gsx · 10-07-2005

Yeah, well i'll probably just run with the 19's. If i hook up right i shouldn't lose a whole lot of wasted tread. FWD cars are much harder on tires than AWD's in my experience.

**Shane@DBPerformance** · 10-07-2005

The A/F ratio in DSMLink is not real. It is a just a calculated guess based on the amount of airflow the MAF is seeing versus the amount of fuel the injectors are spraying. If you have a boost leak or a hacked MAF or a bad line going to the FPR, then it will be way way off. If you want to know your real A/F ratio, you need to get a wideband. An EGT does not tell you if you are rich or lean either, it just tells the exhaust temps, which are more effected by timing than A/F ratio.

niterydr · 10-07-2005

Quote:

Originally Posted by ecoli

The A/F ratio in DSMLink is not real. It is a just a calculated guess based on the amount of airflow the MAF is seeing versus the amount of fuel the injectors are spraying. If you have a boost leak or a hacked MAF or a bad line going to the FPR, then it will be way way off. If you want to know your real A/F ratio, you need to get a wideband. An EGT does not tell you if you are rich or lean either, it just tells the exhaust temps, which are more effected by timing than A/F ratio.

This man knows what he is talking about

.

Onefast99gsx · 10-07-2005

I took it out tonight after work for some more serious pounding. I had to zip tie the hose on because it kept popping off. While the hose was off i was easily seeing 6+ degrees pulled back no problem. Now with it connected, i turned up the boost to about 23psi. I'm seeing about 2-3* being pulled back in the same spot(5700ish). Is it possible that the stock FRP was damaged from the vacuum line not being hooked up all that time? Or is it possible that the stock FPR is no good to run with a rewired 255LPH and 23psi of boost?

Thanks.

Outlaw1 · 10-08-2005

Quote:

Originally Posted by Onefast99gsx

I took it out tonight after work for some more serious pounding. I had to zip tie the hose on because it kept popping off. While the hose was off i was easily seeing 6+ degrees pulled back no problem. Now with it connected, i turned up the boost to about 23psi. I'm seeing about 2-3* being pulled back in the same spot(5700ish). Is it possible that the stock FRP was damaged from the vacuum line not being hooked up all that time? Or is it possible that the stock FPR is no good to run with a rewired 255LPH and 23psi of boost?

Thanks.

If that hose keeps popping off you will be rebuilding your engine in the near future.

23 psi depends on your combination of parts, your tune and of course, fuel quality.

**JET** · 10-08-2005

Knock can also be caused by imperfections in the piston or head surface, which yours may have from running so lean.

No, the FPR wouldn't be damaged from that.

**Shane@DBPerformance** · 10-08-2005

You might want to ziptie every vacuum line on the car, if you are going to run more than stock boost.

Outlaw1 · 10-08-2005

Quote:

Originally Posted by ecoli

You might want to ziptie every vacuum line on the car, if you are going to run more than stock boost.

I second that.

Onefast99gsx · 10-08-2005

All were zip-tied except for that one. My bad. I backed the boost down to right about 20# just a bit ago. I can run her hard 60-90 with just about zero knock. If i go much over 20# like i was doing yesterday she'll start to knock in 3rd gear. Perhaps alky injection is only good in my car to 20psi. Either that or i'm over-running the stock FPR. I was hoping to boost to 23# with alky inj.

**Shane@DBPerformance** · 10-08-2005

Overruning the stock FPR is only a problem at idle/cruise. Your fuel pressure should be at it's highest and hardest to overrun during high boost. If you really want to run high boost on pump gas, then get a methanol injection kit. Water/Isopropyl alcohol injection is a waste of time.

Onefast99gsx · 10-08-2005

Would love to run high boost on pump

As for what i run for injection, it's the same stuff the stock car and drag racers use. I just call it alky. I used to mix it 75/25 but i have so much of it and it doesn't use an incredible amount so now i just run straight 100% alky.

**Shane@DBPerformance** · 10-08-2005

What alky though? If you are using methanol, then you should really get a wideband, because it acts like adding fuel and tuning off of just the DSMLink stuff would be almost about as good as just randomly guessing. Is it virgin methanol you are using? Where are you getting it from? Are you using any upper lube with the methanol? The guys running methanol injection kits are able to run over 30psi on pump gas.

Onefast99gsx · 10-08-2005

Shane- I'm 99% sure it's ethanol, the stuff made from corn. Looks like methanol is made from wood products. I have not been using any kind of upper lubricant. Do you think that ethanol is not nearly as good as methanol? I'm curious to see your answer to that. I got this stuff from a guy that races Late Model stock cars.

Thanks.

**Shane@DBPerformance** · 10-08-2005

Yea, ethanol is not as good as methanol. But it is not as corrosive either. It is better than normal gasoline. Our gas here in MN, I don't know about WI, already had 10% ethanol in it.

Spraying ethanol is like adding more fuel though also, so your DSMLink A/F ratios will be even farther off, if you spray much of it.