NEED HELP! Hilborn injection

[Mathi]

Hi,

I have a Z502 Chevrolet crated engine with a Hilborn fuel injection system on it. It's an electronic fuel injection with Fast ECU and other electric parts.
Now, the injection works perfect only if you stop throttle, there is some bangings in the exhaust . Everytime we stop throttle, there are those annoying bangings. Really loud.
Just like too much fuel...
Now, we tried everything... We contacted Hilborn and they helped us out with some instructions but it was worse after those instructions.

Now, I live in Belgium and we don't know anymore what we can do. We are far away with a system that doesn't work as it should. We have contacted here in our country, the Netherlands, Germany, etc fuel injection specialist but nobody knows this system good enough to help us out.

Can someone help me out?

Thank you!

This fuel injection system:


http://www.hilborninjection.com/prod...=429&CatId=174

[Blown353]

I've experienced this problem on several engines with FAST EFI. Individual runner intakes seem to magnify the problem of exhaust pops during overrun especially if there are sync issues between each cylinder. Get a syncrometer and check each runner to make sure the throttle blades are adjusted properly.

FAST does not have a DFCO (decel fuel cut off) function so the injectors continue to deliver the amount of fuel that is specified in the VE tables during overrun as well as typically adding O2 correction during overrun if you're running closed loop. This causes the engine to run too rich during overrun and leads to popping in the exhaust.

Do some datalogging and while driving run the engine up to high RPM and then completely let off the throttle and coast back down to a near-idle. Look at the datalog see what cells on the VE table are used for overrun then play with the fuel & timing settings in those overrun cells. Usually adding some timing and taking away a lot of the fuel in the overrun cells will take care of the popping issue. Also limit the amount of positive O2 correction fuel in the overrun areas of the O2 limit tables (XFI) or O2 correction limit menu (FAST classic). That will prevent the ECU from adding too much positive correction fuel when the mixture starts reading max lean (15.9 AFR) when you let off the throttle to coast.

Also make sure there are no air leaks in the exhaust system.

[Mathi]

ok, we will give it a try... Will update!

Thanks for your help! I really appreciate it!

[supremeefi]

Very Good info 353 , but sometimes when it's too lean on decel it backfire and burble as well. And as mentioned, timing can be a big part of it too.

Keep us posted Mathi and good luck.

[camcojb]

Originally Posted by supremeefi

Very Good info 353 , but sometimes when it's too lean on decel it backfire and burble as well. And as mentioned, timing can be a big part of it too.

Keep us posted Mathi and good luck.

yeah, I ended up richening mine in the decel areas to stop it.

[GregWeld]

Originally Posted by camcojb

yeah, I ended up richening mine in the decel areas to stop it.

Same here....

It's easy enough to mess with and see which way it works out best - but too lean can pop even more than too rich... and 8 stacks "tend" to be lean because there's so much air and air speed available so quickly. That, of course, is what we like about them!

[Blown353]

Originally Posted by supremeefi

Very Good info 353 , but sometimes when it's too lean on decel it backfire and burble as well. And as mentioned, timing can be a big part of it too.

Keep us posted Mathi and good luck.

Good point-- I forgot to mention that as well. That's what I get for posting in a hurry from work. LOL!

A mixture that's far too lean during overrun can cause the mixture not to burn or not completely burn in the cylinders and instead the unburned fuel will build up and burn/pop in the exhaust.

It does take a little trial and error to find best amount of fuel to greatly reduce or eliminate the overrun pops. Datalogging will at least show you which cells you need to concentrate on for mixture, timing, and O2 correction limit tweaks.

Going too lean in the overrun areas can also cause a "dead spot" in the pedal at very slight throttle angle changes when transitioning out of overrun.

I still wonder why FAST hasn't added a DFCO function after all these years... it's not something that's necessary but it would sure be nice to have-- and it seems like 98% of the other ECUs out there offer it.

[supremeefi]

Originally Posted by Blown353

Good point-- I forgot to mention that as well. That's what I get for posting in a hurry from work. LOL!

A mixture that's far too lean during overrun can cause the mixture not to burn or not completely burn in the cylinders and instead the unburned fuel will build up and burn/pop in the exhaust.

It does take a little trial and error to find best amount of fuel to greatly reduce or eliminate the overrun pops. Datalogging will at least show you which cells you need to concentrate on for mixture, timing, and O2 correction limit tweaks.

Going too lean in the overrun areas can also cause a "dead spot" in the pedal at very slight throttle angle changes when transitioning out of overrun.

I still wonder why FAST hasn't added a DFCO function after all these years... it's not something that's necessary but it would sure be nice to have-- and it seems like 98% of the other ECUs out there offer it.

That's a great question, probably why Accel hasn't added "self learning". Let me tell you why.
I asked Accel a couple of years ago about adding "self learing", the answer is simple.
Most EFI's in this class use the same capacity boards, they'll only hold/do so much, period. Big Stuff has more dataloging than most others out there, but did you ever see their transient fueling tables? They suck, I think there's 3 of them. FAST now has self learning and some other "new" stuff. But again there are other things they had to leave out. Accel doesn't have self learning but has more transient fueling tables than anyone, and have you ever used their nitrous tables? I don't think they get any easier, enter the pill size and bottle pressure and it does the fuel map for you, and it's damn close.
So what do you give up? In the case of Accel, do you give up the transient tables etc that imo make it drive better than anything in this price range, or does BS3 give up their datalogging capacity that makes them a drag racers favorite? Tough choices.

Every system has some limitations, it just depends on what's important to you and your application. I have no trouble tuning the Accel without the self learning feature, I wouldn't give up the potential driveability for anything.