Backfire

[smp3000]

Sup fella's

I was wondering if any of you turbo guys get a subtle backfire.. especially at low rpms and lower gears.

I've noticed that ever since I put the straight pipe in-eliminating the 2nd cat-I am getting a very sublte backfire in 2nd gear at lower rpms.

Is this at all bad? I wouldn't think so, but I'm just not sure what's causing it.

 

[Captain KRM P5]

I hear it sometimes coming through the exhaust system...makes me wonder what the hell it is.

 

[LinuxRacr]

Not yet...I don't believe!

 

[Equinox]

turbo or not if you put a straight pipe in your will start to notice some backfire. It's not turbo related

 

[Stou]

I don't have any cat on my car and I heard backfires only twice since 8 month!

 

[smp3000]

What octane do you have up there in Canada?

 

[big_ben]

Stou, you know what I've realized about your car. You probably have the least amount of problems out of anyone with your turbo system. Those guys at Extreme Machines must really know what they are doing.

 

[20ESGUY]

Yeah with a straight through style exh. you'll get a slight blurp when coming down in the lower rpm's. I can say it's not turbo related cause i dont have turbo...but i get the blupable. BTW it's really not a backfire, it's just from the loss of back pressure in the system, mostly resoance.

 

[spoolinmp3]

I dont get any backfires in lower gears or when driving around town, but under WOT through 1-3 gears I might get this huge backfire that sounds like a shotgun blast. It scares the sh#! out of me sometimes. But it does not happen often.........

 

[DooMer_MP3]

Stou, you know what I've realized about your car. You probably have the least amount of problems out of anyone with your turbo system. Those guys at Extreme Machines must really know what they are doing.

Yeah I've noticed this as well. Him and spoolin had some initial issues (I remember a lot of threads about check valves), but since then they seem to have the most reliable setups.

The BEGI kit has since worried me with all of their pinging/fuel problems. I know it was the prototype, and it seems like FM has a solid fix, but damn, if those kits were on my car in their earlier stages, I would've been scared shitless . However, its nice to see how dedicated Keith@FM is to our community, and for that, I give you a great big thank you!

Chris

 

[blynzoo]

Yeah I've noticed this as well. Him and spoolin had some initial issues (I remember a lot of threads about check valves), but since then they seem to have the most reliable setups.

The BEGI kit has since worried me with all of their pinging/fuel problems. I know it was the prototype, and it seems like FM has a solid fix, but damn, if those kits were on my car in their earlier stages, I would've been scared shitless . However, its nice to see how dedicated Keith@FM is to our community, and for that, I give you a great big thank you!

Chris

AMEN! I second that motion. Thanks, Keith, and everybody at FM!!!!

 

[Stou]

I try to run my car as most as possible with 94 octane gaz. Here, I can get it at Petro-Canada gaz station. If I can't get to one Petro-Canada, I have to get some 91 or 92 octane gaz. But most of the time I run it with 94.

It's true that I don't have problem with my car. It is runing a bit rich but it's not a big deal. It's not rich to the point that you can see black smoke. It only got a small rich smell and my A/F if at 3/4 rich on WOT, so no big deal.

My only other problem is the CEL. Since I don't have cat (the 2 of them) anymore, the CEL is always on..... so I removed the light!

The big difference between Spoolin and my setup vs Begi setup is that we run extra injectors instead of a FMU setup. Maybe the FMU is a bit more difficult to tuned. When I went to Extreme Machine the first time, we discussed about the FMU and extra injectors setup and they recommend me to go for the extra injectors setup and this is what I did.

But don't think that I didn't have problems at first. I got almost the same problems that you got. On the first 2 weeks, I had air leak, prestone leak, oil leak, fuel leak and the problem with the ECU that was freaking out after 5000 RPM (the thing about the check valves). But we worked each problem as they arrived and that was it. After that, everything was fine!

I realy think that the FMU setup is a bit harder to tuned because of the fuel pressure but for the rest, it's the same kind of kit!

They only other big difference is the FM/IC. This maybe can do a difference about the pinging. Spoolin and I have big FM/IC and the Begi kit have a small one. So we are probably runing with a bit colder air......

 

[LinuxRacr]

Per Corky, it is better to have more short runners on the IC, then few long runners. Yeah, I feel ya! I have worked each problem as they came, and it seems I only have one more turbo related problem. The oil leak. I talked to BEGI yesterday. The solution is comming!

 

[Keith@FP]

One note about FMU versus extra injectors - research by Chevrolet on throttle-body fuel injection (ie, a similar setup to running an extra injector or two) showed a 10% variation in fuel delivery from cylinder to cylinder. If you're going to run extra injectors, you should be running one per cylinder. We've tried both ways, and driveability is far better with the four injectors.

An FMU (we call ours an Auxiliary Fuel Pressure Regulator - I don't know what FMU stands for actually) will deliver the extra fuel consistently from cylinder to cylinder to the extent of the abilities of the fuel rail.

No matter what system you use to dump extra fuel into the engine, you need to prevent the stock ECU from pulling that fuel out again when it's running closed loop. That's what was causing the knock problems on the early BEGI installs, and it's why Stou has to tune his car to be so rich. AFPRs are dead easy to tune when you've got the other problems solved.

Thanks for the props, guys. Appreciated. Thanks for the patience as everyone gets a ringside seat into what's involved in making a production turbo kit! I know it's been a bit rocky at times.

Keith

 

[Stou]

Keith, there's one thing I don't understand about that 10% variation. My 2 extras injectors are on the intake tube something like 2 feet before the throttle-body. The gaz is mixed with air before entering in the throttle-body. So how can be 10% variation from one cylinder to another if the mix is done very early in the intake tube?

Are you still out of stock for the "FM O2 signal modifier"? If yes, when do you think there will be some available?

 

[Keith@FP]

I'm not exactly schooled in fluid dynamics, which is why I let Chevy do the research You will notice, however, that throttle body injection is long gone from factory cars.

We're just waiting for the last part for those signal modifiers. They should be on the way, but I've learned from this supplier not to get excited until the box is actually in our hands. There's no answer for you because I don't have any info myself - sorry.

Keith

 

[big_ben]

I can help out on that fluid dynamics since I'm still in school and I have taken that class. THe cylinders will not see equal amounts of fuel or air from a plenum type intake manifold. The only way to make the cylinders get exactly the same amounts of fuel and air are to have individual injectors for each cylinder and individual throttle bodys for each cylinder. When the air is thrown into one chamber (the plenum), there is no way to regulate how much air goes where. Well, I'm sure there are ways to get it close, but they would have to do turbulance testing for years to figure out the perfect internal dimensions to make the air flow equally into each intake port. Most of the air is going to go into to port with the least resistance, this is why there is a "leanest cylinder".