I frankly don't understand why it's so difficult to get properly flow tested, matched injectors with proper offset and upper/lower non linear data. I build and tune Subaru engines for a living and we run between 100 and 200 Lb/Hr injectors as a matter of course and have no issues at all. We run either Injector Dynamics or Deatschwerks injectors and we have flawless idle control and no issues with tuning them whatsoever. A set of 2000cc (190 Lb/Hr) injectors costs around $800 for 4 of them. I doubt anyone on this forum could max out a set of eight 190 Lb/Hr injectors. Maybe I should talk to them about what they can offer us.....

GD

 

Not sure if you guys know but we have the same exact injectors as ID, Deatschwerks, Grams, etc.
We have 550cc, 650, 750, 850, 1000, 1100, 1200, 1300, 1500, 1600, 1700, and 2200cc Bosch injectors.
They all come with data. Unfortunately it's been a nightmare to get the info that you're all looking for with regards,
to the bosch lll's. However we are still working on it

 

Just created an account to comment on this thread, I know it's a few months old. I have a 91 350 L98 Vette with the 7727 ecm, AXCN base, $8D mask, ZZ4 cam, bored out .30 over, Bosch III's 22lb. I've been running into an issue with high BLMs while cruising and low to spot on blms at idle. Engine also feels sluggish while accelerating, sometimes stumbling. Idles fine in Open Loop but drives VERY rough, almost stalls while getting off the clutch normally in 1st. Idles good in Closed Loop @ 750 rpm. Vacuum gauge measure 14" at idle, and fuel pressure is 39 lb's at idle.

Made a few changes last night that I can document here as they pertain to the discussion at hand.

1.) 0'd out offset tables. I also changed the injector pulse width tables from stock to the tables listed in RBob's post #4. This helped a little with BLM's at cruise, but didn't help much with power.

2.) Changed injector constant to 19 lb's based on SouthBay's Post #15, kept the offset table 0'd and the pulse width table at RBob's. Immediately pegged the idle BLM's at 108. Didn't drive around, idle was very rough, engine sounded like it was trying to stay alive.

3.) Changed injector constant back to 22, and changed injector offset to values listed in posts #86 and #87 from this thread:https://www.thirdgen.org/forums/diy-...ors-not-2.html. This is Southbay's injector offset information. So far I've been rich at idle 108-116ish, but spot on 128 at cruising and Butt-O-Meter definitely feels a difference pulling.

4.) Changed Idle VE Tables to smooth out idle based on datalogging, so I could drive to work and not worry about idle. Idle seems happier with BLMs in the low 130's and part throttle is good as well.

So far the offset information that Southbay gave helps the most running anywhere besides idle. Not sure if the idle issues are due to not tuning in the ZZ4, or other issues (I seem to have low vacuum and fuel pressure), however a little idle VE love helped that out.

If you guys have anything I can try and adjust I would be more than happy to datalog and return results.

 

What kind of manifold vacuum are you getting? I have a cam that's a few deg more radical than the ZZ4 and I pull 12 inHg at 650 rpm in gear with an automatic and factory LT1 torque converter, about 15-16 in park. If you're lower than that, then there's likely a problem some place. If you're between that and the factory cam, then it's probably par for the course.

In which case, one might expect the ZZ4 cam to have more of an impact on idle BLMs than anywhere else, and probably means like you're on the right track as far as that goes.

Though what's your fuel pressure? If that's off, it'll also affect things as well...

In any event, you could send me the data log and I'll take a look.

ultm8z@yahoo.com

If you really want to get the inside scoop on how the car is running, you'd probably want to get a WB O2 sensor and start looking at actual AFR's during open loop and power enrichment.

 

I plan on datalogging on my way home from work, so I'll definitely send that, thanks!

Fuel pressure is 39psi at idle, ideal is 41 - 47psi from what I've been told. Vacuum gauge showed 14" at idle, but that wasn't off the manifold, just one of the vacuum lines, so I'll have to check that again.

 

I'll have to double check my vacuum at manifold, I just checked it off one of the vacuum hoses, which pulled 14" at idle. Fuel pressure is 39 at idle. The 91' FSM states 17 - 21 for vacuum stock, and 41 to 47 fuel pressure stock. I'll log data on my way home from work so I will definitely send that, thank you!

 

What's your idle speed. To the first order, It actually sounds about right. ZZ4 cam has ~8 deg more intake duration than the factory, so you should expect some decrease in idle vacuum.

Your fuel pressure is with the vacuum connected or disconnected?

 

Idle speed was 750 RPM. Awesome, that's good know. I tested the fuel pressure with the vacuum disconnected. I also R&R's the fuel rail, bought a new fuel pressure regulator, and filter two years ago, as well as replaced the fuel pump maybe three months ago. Also odd thing about the fuel pressure, after the pump primes, it drops to 0 within 20 seconds.

 

Sounds like an internal leak in your fuel pressure regulator. The fuel pressure is a little low too... probably want to bump it up to around 42 psi with vacuum disconnected.

 

I did replace the diaphragm maybe 2 years ago, but if it had an internal leak wouldn't it fill the attached vacuum hose with gas? I've checked mine while testing the fuel pressure before and it smelled faintly like gas but I couldn't see any gas present. I don't have an adjustable fuel pressure regulator so I guess I should invest. Is there a way to pick up the pressure without one?

 

If you're running the stock FPR, then you're essentially stuck with the fuel pressure as it is.

Either the FPR is bleeding off pressure or one of your injectors is leaking fuel into the manifold. It shouldn't be bleeding off pressure like that with the engine off.

 

Good to know, I'll follow steps to test the FPR and injectors, and replace what's necessary. Thanks for the info, sorry to derail from the topic at hand. I also support making a sticky for the Bosch III's offset information, always good to know there's a little more tuning to done.

 

I’m curious what the before and after numbers are.
When you get time please post them so everyone can see the effects of the offsets being changed if any.

 

I have a set of gen4 36pph Bosch's coming to replace damaged 280155737, I'm using EBL Flash- what do I need to do to format this table into what I need? Don't have a part number yet.

Manifold Vacuum kPa {link: GM.MANVAC} 0
4.5 7.285745
5 7.169087
5.5 6.218478
6 3.962941
6.5 2.573279
7 1.939834
7.5 1.574168
8 1.309082
8.5 1.114422
9 0.954994
9.5 0.827989
10 0.725101
10.5 0.646214
11 0.573173
11.5 0.500671
12 0.435207
12.5 0.386359
13 0.339858
13.5 0.292894
14 0.24897
14.5 0.212892
15 0.176967
15.5 0.141236
16 0.108773
16.5 0.080887
17 0.054694
17.5 0.029539
18 0.011423

 

Easy, just fit the numbers to the GM voltage scale:

INJ - Injector Correction Offset:

0 Volts: 386 usec
1.6 Volts: 7280 usec
3.2 Volts: 7280 usec
4.8 Volts: 7210 usec
6.4 Volts: 2800 usec
8.0 Volts: 1310 usec
9.6 Volts: 828 usec
11.2 Volts: 535 usec
12.8 Volts: 360 usec
14.4 Volts: 225 usec
16.0 Volts: 109 usec
17.6 Volts: 30 usec
19.2 Volts: 30 usec
20.8 Volts: 30 usec
22.4 Volts: 28 usec
24.0 Volts: 28 usec
25.5 Volts: 28 usec

I would then graph it (in TP) just to double check for any jumps in the data. Smooth as required.

RBob.

 

Hello Robert and thanks for that, taking another stab at tuning the truck. Spent some time re/re heads to establish TDC for timing mark, found a large oil leak at the rear china wall, pcv is sucking some oil, and best of all when the shop 'fixed' the WB (time I paid for btw) I found they cooked the controller and just soldered all the wires together- no wonder I was having a hard time with VE learns last year. You may remember your supplied tune was far better than what I ended up with. I'll supply injector part number here when I get it- to help anyone else out.

 

Looks like this thread hasn't been sticky-fied yet?? Any reason not to do that?

 

Sorry guys this is all I have, part number ground off.

 

?

 

That’s odd, can you email the company you purchased them from for the part number and or possibly the offsets ?

 

I checked 4 of them, all ground off. Also giving me a headache leaking from the rail- I've replaced many injectors and have had no issues, waiting for the clips and see if that solves the issue. They did supply info as above.

 

If the injectors are leaking from the fuel rail...it's either the orings, the way you installed them, or they're too short. Did you put them into the intake first or the rail?
Are they the bosch lll's?

 

These are Bosch4's, these are replacing a set of yours- I had damaged one. I tried installing then any way possible- I prefer in the rail first as I find the rail has some sharp edges I would rater keep the o-rings away from. I just bought new O-rings specifically for TPI/LT1 perhaps whatever came with them is slightly different. I also used SilGlide lubricant and now switched to soap. There was also machined spacer rings that ride on the bottom shoulder of these injectors. The intake is FIRST TPI with the GM rails machined to fit. The fuel rail bungs are not fully machined through and I could see that with using the rings the top o-rings were deformed against the remaining unmachined surface. I think by using the clips as a 'datum' for the top and let the bottom o-ring seal where ever should fix the issue......just waiting for clips as I haven't had a need for them in the past. Note for other's when doing injector work- pressurize the system with the runners off- saves alot of work if you have problems.

 

ugghh...I wish you would have contacted us. We could have fixed that for you in 2 seconds.

 

I've used the bosch4's in a smaller build- I liked them, didn't like the adapters to USCAR.

 

Well between the injectors and clips it cost a month waiting. Installed clips- no more leaks.
I think the data is suspect- barely runs and when I use the old offsets- runs OK.

 

just to add another experience that supports this conclusion... over the past couple years i have used bosch iii in several of my 3rd gens as i have needed to rectify issues or rebuilds with new crate motors etc

with the new crate motor upgrades i went with EBL for the controller and needed to put in the injector data to start and the data provided by RBob worked well and had good luck

i have a couple of 3rd gens though that i just replaced with the injectors and while they have been running the BLMs have not been great. I finally got enough time to take a look at one of them, my 89 IROC vert with stock 305 TPI LB9 / T5. this has a completely rebuilt fuel system from a couple years ago including Bosch III white "19lb" replacements. Sure enough some data logging showed BLM maxed to 160 in several areas. Also it has hard cold cranking so i wanted to adjust that as well.

I basically followed what ULTM8Z and GeneralDisorder recommended in other threads with great results. Pic shows the changes, i ended up using 17.5 as the injector flow rate and resulted in basically solid 130 BLM with great engine response across the rpm/load range and also great cold starts now

Also there appears to be a great new OBD1 scanner available from TunerCat called DataCat. I have only used it this weekend, but it is a huge improvement over DataMaster (especially considering the license problems now that they aren't supporting it, etc)... i was very impressed with it and already bought my full license for it

http://www.tunercat.com/

 

 

don't forget thirdgen members receive 10% off. The damn promo code has not been working on our site...however we definitely honor it if you call us at the shop until we get this issue fixed.
Hope this helps

 

 

My pleasure. Well if you decide at any time to send them in just let us know

 

To be fair - it isn't the "damn injectors" that are the problem. Not at all. It's that they are so much more advanced than what the car originally came with, and different in design that they require different programming to work (perfectly). From the voltage offsets, to the spray pattern, they are very different. When measuring the raw max flow rate they are SIMILAR to the originals. That, and having the same electrical plug is about all they have in common really. Oh yeah - they spray gasoline.

As with many things - they are an adequate substitute without any tuning for some applications and for the less-discerning among third gen owners. Many people just write off their behavior as quirks of a 30 year old vehicle, believe the behavior is related to something else, or just aren't even aware that it's not supposed to do that (long crank, poor cold operation, sub-par throttle response, etc). Many people just assume that cars worked that way in the 80's.

GD

 

 

It really isn't all that difficult to exchange a few prom chips with a tuner, but yours is a fair point.

The Delphi injectors are probably a closer match, but are still newer technology and may still require some tuning modifications to be entirely perfect.

The unfortunate reality is that the original injectors were poor quality, and are no longer made. And some tuning is virtually unavoidable if you want to use newer technologies. Even changing to a mini-starter technically may require tuning for the faster cranking RPM as this has an effect on the fueling required per reference pulse.

GD

 

 

i would say without the specific tuning it is definitely operable, but everything is relative... ie when you are having a fuel problem already with the original injectors and then get it running by swapping in some bosch iii's your impression can be big improvement as you are back in biz. however it is quite apparent that a little tuning really goes a long way to provide great starting, idle, and drive ability... can't believe i put up with it so long versus just addressing it!

 

I've had Bosch 3's from Southbay on my Monte Carlo SS 350 TPI conversion for several years now. MAF setup. After I first started the car and broke in the motor, the BLMs were pegged at 160. Since then I have read many posts by members of this forum and have tweaked several parameters in the tune. The last time I checked, my BLMs hovered around 128 - 140. Not perfect, but I'm getting there. Thank You ThirdGen for your knowledge.

 

glad this thread is paying some dividends...

 

Per the other stickies it appears the admin for DIY PROM is 3.8TransAM.

 

I'm running the same injectors as you. Where did you get those offsets? Here are the ones RBob gave me:

Offset Compensation versus Battery Voltage:
6.4 Volts: 3193 usec
8.0 Volts: 2163 usec
9.6 Volts: 1618 usec
11.2 Volts: 1278 usec
12.8 Volts: 1031 usec
14.4 Volts: 821 usec
15.0 Volts: 784 usec*

 

My data came directly from Ford...

http://performanceparts.ford.com/par...9593-bb302.pdf

One of the main reasons I bought this particular set... It had OEM factory data to back them up...

Numerous websites also confirm the p/n interchange.

 

Awesome! Thanks for sharing.

 

The admins and the moderators are two separate functions. This thread has been stuck in the Tuning Guide Book thread. There are three moderators for the DIY_PROM forum.

RBob.

 

The reason for the discrepancy is that the injector compensation needs to take into account the fuel pressure. You can use just the offset compensation ( FNPW_OFFSET) and get reasonably close. It beats all to heck of not having any offset data.

I took it a step further and do the fuel pressure compensations to come up with the final values. Although it doesn't match the GM way of doing both the offset and small injector PW compensations.

RBob.

 

OK great I thought this should be stuck somewhere and didn't notice it had been.

 

I personally have no complaints. Car has run great for years since you gave me those values to plug in.

 

 

 

Do you have this same data for the 0 280 155 830 Dlll injector you sell. I just purchased a set and was hoping the data would be included with the purchase.

 

That type of information is not included with the D-III's and honestly may not be that useful in practice anyway (the offsets I've found haven't been especially useful). Best thing to do is test the injector latency on the car in the *exact* configuration and environment where it will be running. Unfortunately a 2-channel (at a minimum) lab scope is required to do this. USB lab scopes have come way down in price though.

GD