Idle surge with bigger injectors

93White3400Z · May 03, 2008, 11:50:24 PM

So yeah, I'm sure I'm not the only one in this situation. With bigger injectors then stock, it cause a rich condition at idle which make the engine run crappy. BLM and INT are at 128 and my wideband show 14.7 but I know it's crazy rich because the odor of gas is there for sure :icon_lol: and i even got knock sometime.

I've heard what can cause something like that is the too large BPW (Base Pulse Width) at idle because of the larger injectors (28lbs instead of the stock 22). My question is where is that BPW that I could change (lower at idle) to make my engine run better ? If anyone have an address for the BPW table or something that could correct BPW, that would be awesome.

Btw, thats on a turbo 3400 in a 93 z24 but it shouldnt matter, my problem is chip related and i'm using 8F.

Thanks to anyone that want to help :icon_wink:

flybynite · May 04, 2008, 06:33:36 AM

Quote from: 93White3400Z on May 03, 2008, 11:50:24 PM
So yeah, I'm sure I'm not the only one in this situation. With bigger injectors then stock, it cause a rich condition at idle which make the engine run crappy. BLM and INT are at 128 and my wideband show 14.7 but I know it's crazy rich because the odor of gas is there for sure :icon_lol: and i even got knock sometime.

I've heard what can cause something like that is the too large BPW (Base Pulse Width) at idle because of the larger injectors (28lbs instead of the stock 22). My question is where is that BPW that I could change (lower at idle) to make my engine run better ? If anyone have an address for the BPW table or something that could correct BPW, that would be awesome.

Btw, thats on a turbo 3400 in a 93 z24 but it shouldnt matter, my problem is chip related and i'm using 8F.

Thanks to anyone that want to help :icon_wink:

Set the injector flow rate to 34.5lbs. Then start removing fuel at idle rpms in the base ve vs rpm table located at 07AF. Once idle is fine start working up to 3k. When you have that done work on 3k-6k and you should be fine... If your BLM is 128 and your INT is 128 at idle you should have an AFR of 17 to 1...Good Luck
Adam

meltboy11 · May 04, 2008, 08:18:26 AM

Quote from: flybynite on May 04, 2008, 06:33:36 AM
Quote from: 93White3400Z on May 03, 2008, 11:50:24 PM
So yeah, I'm sure I'm not the only one in this situation. With bigger injectors then stock, it cause a rich condition at idle which make the engine run crappy. BLM and INT are at 128 and my wideband show 14.7 but I know it's crazy rich because the odor of gas is there for sure :icon_lol: and i even got knock sometime.

I've heard what can cause something like that is the too large BPW (Base Pulse Width) at idle because of the larger injectors (28lbs instead of the stock 22). My question is where is that BPW that I could change (lower at idle) to make my engine run better ? If anyone have an address for the BPW table or something that could correct BPW, that would be awesome.

Btw, thats on a turbo 3400 in a 93 z24 but it shouldnt matter, my problem is chip related and i'm using 8F.

Thanks to anyone that want to help :icon_wink:
Set the injector flow rate to 34.5lbs. Then start removing fuel at idle rpms in the base ve vs rpm table located at 07AF. Once idle is fine start working up to 3k. When you have that done work on 3k-6k and you should be fine... If your BLM is 128 and your INT is 128 at idle you should have an AFR of 17 to 1...Good Luck
Adam

uh...ya, what he said... :thinking:

93White3400Z · May 04, 2008, 03:01:31 PM

Quote from: flybynite on May 04, 2008, 06:33:36 AM
Quote from: 93White3400Z on May 03, 2008, 11:50:24 PM
So yeah, I'm sure I'm not the only one in this situation. With bigger injectors then stock, it cause a rich condition at idle which make the engine run crappy. BLM and INT are at 128 and my wideband show 14.7 but I know it's crazy rich because the odor of gas is there for sure :icon_lol: and i even got knock sometime.

I've heard what can cause something like that is the too large BPW (Base Pulse Width) at idle because of the larger injectors (28lbs instead of the stock 22). My question is where is that BPW that I could change (lower at idle) to make my engine run better ? If anyone have an address for the BPW table or something that could correct BPW, that would be awesome.

Btw, thats on a turbo 3400 in a 93 z24 but it shouldnt matter, my problem is chip related and i'm using 8F.

Thanks to anyone that want to help :icon_wink:
Set the injector flow rate to 34.5lbs. Then start removing fuel at idle rpms in the base ve vs rpm table located at 07AF. Once idle is fine start working up to 3k. When you have that done work on 3k-6k and you should be fine... If your BLM is 128 and your INT is 128 at idle you should have an AFR of 17 to 1...Good Luck
Adam

where the 34.5 came from ? and what do I need to set the injector rate per single fire to ?

What injector did you have in your TGP ? Any surge ?

flybynite · May 04, 2008, 03:38:37 PM

OK I'm running 28lb ls1 style injectors. When I first started tuning this set up I set my injector constant to 28lbs. With lots of work I got the cruise and WOT pretty good on the wide band but the idle stayed rich. When I got to a point that I could not remove any more fuel from idle I started raising my injector constant. At 34.5lbs I found plenty of room for adjustment to the idle Afr. With that good I started re-tuning part throttle with the base ve vs rpm table. Then I fine tuned it with changes to the main ve table. So now that my idle and part throttle are good and verified by the wide band it was time for WOT. As for the single fire mode I do not think it's utilized in stock form. If I remember correctly it's a flag that has to be turned on to use.

93White3400Z · May 04, 2008, 04:06:09 PM

Nice, thats exactly what I wanted to know :icon_biggrin: I will increase the injector flow rate constant :icon_wink: Would you be interested in sending me your bin file since we have a very similar setup even if I have a 3400. AE and decel enleament and everything should be close from what I need. that would really help if you could send it to me.

Thanks! :icon_biggrin:

93White3400Z · May 04, 2008, 04:15:48 PM

Oh and while I'm thinking about it, you put it at 34.5 but I guess you have the 39psi fuel pressure at idle ? I have 49psi fuel pressure so my injector are around 31lbs at 49psi so I would put my constant at like 37.5 (34.5+(31-28)) ?

flybynite · May 04, 2008, 05:33:11 PM

Quote from: 93White3400Z on May 04, 2008, 04:15:48 PM
Oh and while I'm thinking about it, you put it at 34.5 but I guess you have the 39psi fuel pressure at idle ? I have 49psi fuel pressure so my injector are around 31lbs at 49psi so I would put my constant at like 37.5 (34.5+(31-28)) ?

That should be a good starting point. Just make the wide band happy and all will be good... Good luck with your tune.. :icon_mrgreen:

cobracmdr · May 05, 2008, 05:58:12 AM

Hmm now I know what you are doing in my chip adam ;)

93White3400Z · May 05, 2008, 10:16:32 AM

I tried both 34.5 and 37.5 injector flow rate and it didnt do anything :icon_mad: :icon_frown: Not sure what to do now :icon_cry:

flybynite · May 05, 2008, 04:00:09 PM

Quote from: 93White3400Z on May 05, 2008, 10:16:32 AM
I tried both 34.5 and 37.5 injector flow rate and it didnt do anything :icon_mad: :icon_frown: Not sure what to do now :icon_cry:

It made no difference. A change that major should have done something. What was the Afr at idle before the changes and after? What ecu(xdf for tunerpro) are you using?

TGPilot · May 11, 2008, 06:48:47 PM

Where is your wide band located in the exhaust? Where is your narrow band located?

Why would a BLM and INT of 128 be 17:1 AFR? On these old PCMs 128 BLM = 0 trim rate or Stoich 14.7 or whatever your commanded AFR stoich ratio is. Now I have seen 3 or 4 7727/7730 ECMs hold at 128 BLM and 128 INT when the 02 has failed to respond 4 consecutive times. It remains in a constant open loop and only fuels off of the VE table. That was a pig rich bitch! ;)

cobracmdr · May 12, 2008, 08:25:04 AM

Quote from: flybynite on May 05, 2008, 04:00:09 PM
Quote from: 93White3400Z on May 05, 2008, 10:16:32 AM
I tried both 34.5 and 37.5 injector flow rate and it didnt do anything :icon_mad: :icon_frown: Not sure what to do now :icon_cry:
It made no difference. A change that major should have done something. What was the Afr at idle before the changes and after? What ecu(xdf for tunerpro) are you using?

Adam maybe he is having the same problem we had last friday where the idle fuel is based on EGR position? I had no EGR so we had to change it to run off of the injector flow rate. Before Adam did this we made huge changes to the injector flow rate with no response......and I was 10.5 to 1 at idle. If your egr is deleted this could be your problem.

flybynite · May 12, 2008, 02:21:56 PM

Quote from: TGPilot on May 11, 2008, 06:48:47 PM
Why would a BLM and INT of 128 be 17:1 AFR? On these old PCMs 128 BLM = 0 trim rate or Stoich 14.7 or whatever your commanded AFR stoich ratio is.

If idle conditions are met for x amount of msec in closed loop the computer will lean things out past 14.7 I believe they did this to heat up the catalytic conveter for emissions...

93White3400Z · May 16, 2008, 01:46:14 PM

Quote from: cobracmdr on May 12, 2008, 08:25:04 AM
Quote from: flybynite on May 05, 2008, 04:00:09 PM
Quote from: 93White3400Z on May 05, 2008, 10:16:32 AM
I tried both 34.5 and 37.5 injector flow rate and it didnt do anything :icon_mad: :icon_frown: Not sure what to do now :icon_cry:
It made no difference. A change that major should have done something. What was the Afr at idle before the changes and after? What ecu(xdf for tunerpro) are you using?

Adam maybe he is having the same problem we had last friday where the idle fuel is based on EGR position? I had no EGR so we had to change it to run off of the injector flow rate. Before Adam did this we made huge changes to the injector flow rate with no response......and I was 10.5 to 1 at idle. If your egr is deleted this could be your problem.

My egr is deleted. Care to explain a little more ? What did you do to fix it ? I bought a megasquirt but I'm still not sure I want to use it :icon_lol: