E4ME questions

[UKPaul]

Hi,
I need to know the size of the primary jets fitted as stock in the E4ME carb (17081228). If anybody knows what they are could they let me know, otherwise I'll have to strip the carb to find out?
The reason I need to know is that I think my mixture is a bit weak after fitting Headers to the existing duals. I also added an "H" pipe which probably also helped improve exhaust scavenging. So, rather than fit a Holley, etc, etc, I'm going to try & richen up the E4ME to compensate. As far as I can tell, non computer Q-jets usually have to go up 2 sizes in primary jets & maybe fit richer secondary rods (CH as stock?) to compensate for the mods I've done. I've never seen any mention of anybody brave (mad?) enough to try this, but it's worth a shot (afterall, what is there to lose???).
If anybody has modded an E4ME in this way I'd like to hear about it

 

[Yoda]

Paul,

Send a PM to stingray6974 or email him. Mike has rebuiilt more quad than most people have seen I'll also bring this thread to his attention

Bud

 

[UKPaul]

Thanks Bud!

 

[Stingray6974]

Hi Paul,
I'm not familiar with any larger jets availible for this carb. The 350 is the largest engine it was used on. If you changed jets the computer would compensate and adjust the M/C dwell so nothing would be gained. Changing to a smaller secondary metering rod is a good idea.

Mike

P.S. Hi Bud!

 

[Hib Halverson]

I think the first thing you ought to do is determine if, in fact, the engine is really lean at part throttle. What makes you feel the car is lean on the primary side?

Are the OE engine controls functioning? Has the check engine light been on?

Have you already changed the air/fuel ratio at WOT with changes to secondary rods or jets?

 

[67HEAVEN]

Paul,

Nothing to add here, except, "Top of the morning!"

Cheers,
67HEAVEN

 

[UKPaul]

Thanks for the replies I think it's running a bit lean as the exhaust note sounds a bit flat. It's lost the "rich" sound since fitting Headers & an "H" pipe. This is really hard to explain, but it sounds like other engines I've had to richen up. It also feels like it's got less pull than it could have. Again, it's very hard to explain, but after 25 years of playing with engines I've just got the feeling that it's not quite right. I hope I'm wrong as I really don't want to get involved in modifying the E4ME!!!
The computer is fine, check engine light works, etc, etc. I'll be buying one of those A/F gauges that plug into the O2 sensor to verify whether it's running OK & will also check it's output as it may not be hot enough being located in a collector. I'll also change the secondary rods which may be all I need to do to sort it out. I've been told that DA rods should get the secondary mixture about right. Hopefully that will do it on it's own, but I figured that getting some primary jets prior to starting on it would be sensible. If I've got a selection then I could get the job done in a day. If I don't have any & find that I might need some then the job could take 2 or 3 weeks
I'm not worried about the secondaries but the primaries could be awkward if I need any adjustment. Talking to another L81 owner who has measured the O/P from his O2 sensor it seems that there is room for error in the system ie. the mixture has to be way off before the check engine flashes on. I'm hoping that if I need to richen the primaries then just raising the rich stop will do it. If not then I'd like to go up in size on the primary jets to see what happens. It may cause the computer to freak, but it may also result in big smiles all round What I'm thinking is that there might be so much air going through the engine due to the exhaust & cam that the computer can't quite keep the mixture rich enough with the carb set up as stock. As the system only changes the M/C solenoid 10 times/sec then there must be some leeway for error in there as it won't be 100% perfect all the time. So it could be running a bit weak, but not weak enough to throw an error up? Besides, I like to experiment with things Does that sound logical, or am I on the wrong track here???

67Heaven, a jolly good day to you as well, sir! Top notch and all that How are you?

 

[gedmeyer]

While we're on this topic, can anyone tell me the CFM of the E4ME carb on our cars? I was talking about it with a buddy the other day and I couldn't give him a number.

 

[Hib Halverson]

Do not make changes in air/fuel ratio based on engine sound. I'd find some other, more accurate way to determine what the engine controls are doing after you put the headers on. If the system is running correctly and you're not seeing the check engine light, then there would seem to be enough bandwidth in the 81 system to compensate for the headers. If you change the jets or the rods on the primary side, all that will happen is the engine controls will simply lean the engine back out or, go to the end of the fuel trim range, then set the light. What may need to change is the calibration and calibrating 81s might be a lost art at this point.

The problem with the electronic carb is that because of its computer controls, you can't just make a jet change like one could do with older Quadrajets.

E4ME is 750 cfm. In that respect, the electronically controlled QJ is no different than most other QJs since 65 which are 750s. There were, however, a few very rare 800s used on early 70s Buicks and Cadillac.

 

[UKPaul]

Hib,
Thanks for the reply. I know the sounds of the exhausts being used as a basis for playing with the carb sounds a bit dodgy, but it really does sound weak at WOT. There's also a noticeable drop off in power when the secondaries open compared to what it was like before Headers & the "H" pipe were fitted.
I've just ordered a pair of secondary rods to richen the mixture & an A/F guage to hang off the O2 sensor to see what is actually happening. I've no doubt that the primaries are within range to give the correct mixture when only running on them (no Check Engine errors & dwell is OK). But when it goes to WOT (secondaries open) the ECU goes into open loop & requests the max rich postion for the primaries, the secondaries acting as a complement to them. Because it's in open loop then there'll be no error detected by the ECU if it's lean. So I'm thinking that, if the secondary rods don't fully cure it, then slightly bigger primary jets could be the answer. As long as I keep them small enough that the primary mixture limits are within range for the ECU, then it could work out OK. ie the ECU will lean out the primary mixture, as you say, but there will be enough fuel supplied by the jets when the system goes into open loop at large throttle openings (experimenting with the rich stop will probably be needed).

I'm hoping that by just changing the secondary rods it'll have the correct mixture, but it may not work out that simple. I'll post the results when I've finished as there seems very little knowledge on tuning E4MEs to cope with exhaust/cam/etc changes (most advice is to scrap the computer, fit an earlier HEI & a Holley). The rods & gauge are on a 45-90 day delivery time, so it could be a while before I start looking at it!
rgrds
Paul

 

[Hib Halverson]

Hib,
(snip)
but it really does sound weak at WOT. There's also a noticeable drop off in power when the secondaries open compared to what it was like before Headers & the "H" pipe were fitted.
Paul

I believe in your first post you just said the engine sounded lean and I assumed that to mean during ordinary driving when the primary side of the carb is the main contributor to air-fuel ratio.

If the problem is at WOT, then, yes, the engine controls are technically, still in closed loop but ignoring the O2S inputs and fuel trim values.

If the lean mixture can be corrected with a modest change in secondary rods, that is the best way to go.

A change in secondary rods should not alter the carb's calibration when in closed loop---but I'll add that I have no field experience with the E4ME and my understanding of how it works along with my advice may be faulty.

 

[UKPaul]

Hib,
Everything that I've heard/read says that whatever I do with the secondaries won't affect the computer when in open loop at WOT.
I'm fairly confident that different secondary rods will cure any lean condition at WOT, but I'm not convinced that the computer is able to control the primaries to maximum accuracy. Everything that I've read about the operation of it suggests that it's a very accurate & efficient system. No doubt it is when everything is stock, but talking to another '81 owner who has also done some mods has given me some doubts. He's done a lot of measuring of the O2 sensor output & the ECU control to the M/C solenoid & it appears that the ECU is fairly forgiving of incorrect mixtures. It also needs to read a lean or rich condition for quite a long time before flashing up an error code. The ECU must have a "window" around the ideal mixture where it will not throw up any errors, so it could be that mine is running slightly on the weak side (but still within the window of acceptable error), so no error is thrown up & all appears to be OK.
When the A/F gauge arrives I'll fit the new secondary rods & then hook up the gauge (after checking the O2 sensor output seems valid). It'll be an interesting exercise at least & I'll post what I find.
Cheers

 

[Hib Halverson]

Hib,
(snip)
but I'm not convinced that the computer is able to control the primaries to maximum accuracy. Everything that I've read about the operation of it suggests that it's a very accurate & efficient system. No doubt it is when everything is stock, but talking to another '81 owner who has also done some mods has given me some doubts. He's done a lot of measuring of the O2 sensor output & the ECU control to the M/C solenoid & it appears that the ECU is fairly forgiving of incorrect mixtures. It also needs to read a lean or rich condition for quite a long time before flashing up an error code.

That is because of the very slow processor speed. By today's standards, you could benchmark the 80CA/81Fed system with a sundial but, 22 years ago, it was leading edge stuff. To be honest, short of a complete DIY re-engineering of the hardware and a rewrite of the software, you're not going to be able to change that.

The ECU must have a "window" around the ideal mixture where it will not throw up any errors,

You are correct.

so it could be that mine is running slightly on the weak side (but still within the window of acceptable error), so no error is thrown up & all appears to be OK.

You are correct in that theory but, even if the AFR in closed loop is a little lean, the system compensates by adding extra fuel. Because you've got no light on, clearly the system is working within its bandwidth in closed loop.

When the A/F gauge arrives I'll fit the new secondary rods & then hook up the gauge (after checking the O2 sensor output seems valid). It'll be an interesting exercise at least & I'll post what I find.
Cheers

What you really need is a scan tester that will work with the 81 system. That will enable you to look at the short- and long-term fuel trim values--back in ancient times they called those quantities "integrator" and "block learn". Knowing what those figures are in closed loop will tell you exactly where the system is in relation to stoch.

What kind of service information do you have for that car?

Lastly, your idea of pitching the computer controls, back-dating the ignition to a non-computer HEI then bolting on a "dumb" carburetor might not be a bad idea if you're going to continue to modify that car.

 

[UKPaul]

Hi Hib,
Thanks for the reply. The only mods that I intend to do in the future are to fit a set of decent heads to it (preferably AFR180's). I'm not after something that will beat most things on the road, just something that runs well & still has good economy & road "manners". I intend to keep the CCC system in place because I actually like it!!!
I read all the info I've got on the system & saw an interesting fact:
To set a mixture fault code (rich or lean condition) it has to be at road load, in closed loop & at part throttle for up to 5 mins!

This is interesting as it would seem to imply that it could be running slightly lean without flashing up a fault during normal use (it's very infrequent that I can cruise at a constant speed for long enough to set a fault). A scan tester would be ideal, but they're probably rarer than Hen's teeth here What I'll do is get the A/F meter hooked up & also place a dwell meter in the car. By seeing what both are doing I may get an idea of what's going on. If I get nowhere then I could hook up a storage scope to the M/C test lead & the O2 sensor & get exact readings of what each is doing, but that's a bit extreme If I find that the ECU is giving a dwell that's erring towards the rich side I'll do some experimenting with the position of the rich stop & see what happens. Raising the rich stop will richen the mixture on cold start (not a problem) & at near WOT open loop operation but, as you say, the ECU should compensate for it in closed loop operation.
Thanks for the reply

 

[Hib Halverson]

A scan tester would be ideal, but they're probably rarer than Hen's teeth here

Look on eBay for a Vetronix Tech 1 or Tech 1A. You also need the 5-pin to 12-pin DLC adapter needed to connect to an 81 along with any T1 GM Powertrain cartridge. I think they all go back to 81.

Good luck.

 

[tazdevl35]

Hi, Just a thought here but has anyone considered the lost of backpressure due to the now unrestricted exhaust.Usually there is a loss of performance in the bottom end range.Problem is once you unrestrict the exhaust past a certain point you must add fuel and air on the intake side to compensate.My suggestion is a mild cam, better heads and better intake You can richen the rich and lean stops on the carb but only to a certain point then the "window" will be beyond the MC solenoid's ability to control the fuel trim. Also, sometimes a new o2 sensor can help out a bit esp. if the range of reading is shifted. You can make a C3 carb and Dist setup run very well for the street as long as you follow the rules. As far as carbs go less is always better...most engines run their best a little under-carbed..as opposed to bolting on a 1050 holly to a stock engine. Just dont go too lean! Stock is fine. These engines were designed to run with a certain ammount of backpressure to run their best. If you remove too much backpressure you WILL loose performance unless you add more air and fuel to the other side....ie. cam, intake ,heads. If you have questions fell free to contact me and we can go more in depth.


Taz

 

[Vader]

With those replacement secondary metering rods, you might want to consider a hanger change. Between those two items, the secondary metering rate can actually be controlled fairly accurately.

Personally, I've about given up on the CCC, and am just about ready to convert to a '165 ECM from a later car (along with the appropriate injection and harness). Actually, a '730 (underhood version '165) would be the easiest swap, but I'm torn between a MAF and speed density system. I can program anything for these later ECMs, but can't find ANY support for the CCC systems. Reverse-engineering the system would be pointless, since it would still be an old, inefficient, slow system with limited I/O and fuel/spark mapping. There are hundreds of these ECMs and harnesses lying around junk yards being crushed every day.

The car is actually currently running on an '865 ECM from an '84 Camaro, and already has benefitted, but there's so much more potential.

 

[Vader]

OOPS! In my ramblings, I forgot to add this:

 

[UKPaul]

Thanks for the replies people The Vette is now off the road till Spring so I can't check it out until then.

Vader, hopefully I'll be able to get the secondary metering correct with juggling rods & hangers around. I've got some CE rods from Edelbrock but really want some DA rods (still listed by GM). Hopefully a pair will arrive by next May.....
I'm hoping that the primaries will only need minor adjustments to get them in the right ballpark. Mike from this forum has very kindly sent me an E4ME (thanks again Mike ) so I'll be able to swap from a stock carb to a modified/adjusted one to verify changes, etc, etc.
I'll let you know how it goes sometime aroung May!!
Hib, Thanks for the info.

Taz, the loss of backpressure (better scavenging) is precisely what I'm trying to compensate for. On the intake side I've got a K&N filter & Performer intake. There's no emission systems left in place other than the charcoal cannister (which isn't correctly hooked up). There's a mild cam fitted, Headers & duals so, going from past experience with engines, there'll be more gas going through the engine & the carb will need to supply a bit more fuel to compensate. The stock heads are now the biggest restriction in there (and the low CR won't help), so I'm hoping a few tweaks will get the mixture back into the ballpark. If the carb/ECU can't handle the increased flows when I fit new heads then I'll have to rethink it at the time. Maybe EFi???
Thanks all. More next May!
Paul

 

[mikejpss]

UKPaul-You are welcome on the carb donation- It's a good feeling to know I'll have a transplanted "organ" from my lil red thats running around the UK. Happy carb-ing and Merry CHRISTmas . Mike J.