what would you do? EFI problems

[rfuerst911sc]

Well a little over a year ago I started my journey to EFI conversion. I had a good running 83SC with CIS but I didn't like the way it looked. After much research I decided to purchase TWM 46MM throttle bodies,Megasquirt ECU and all the goodies that go with it. Well one year later my car runs like crap. I have searched the MS forum and have talked with smart people but so far no go and I'm tired of screwing with this setup. I can't get it to idle consistantly, it's pig rich, sometimes won't start hot but sometimes will and on and on. I'm running a wideband 02 and she's 10.1-1 at idle!!! I've messed with vacumn cannisters,timing,grounds,tuning etc. with no results. My mechanic is not familiar with MS and won't touch it and neither will the various local tuners with dyno's. So what are my options? Well I can have my mechanic install a ECU he's familiar with like TEC3 or I can rip it all out and go with carbs. I'm not going back to CIS. So any local tuners in Central Florida that can lend me a hand? Or I'll take any constructive suggestions as I want to drive my car again. Thanks

[RarlyL8]

What would I do?
I would sell all that crap and slap on a set of PMOs. EFI is WAY overrated on this board. A lot of money for nothing and a nightmaire to tune. CIS is a good system when the components are new or rebuilt. All systems suck when they are old and worn out, even EFI.
But that may not be constructive advice for you, only my opinion.
If you are in love with the idea of EFI and ITBs you should ship your car to an EFI tuner that has proven experience in the EXACT system you are using. Yes it will cost you a fortune. Knowbody seems to include the cost of tuning in their discussions of how great EFI is. To do it right you need multiple dyno runs and a ton of time spent tuning for an infinite number of variables.
Seriously, if you love a clean engine and a great throttle response consider PMOs. The drawback? Fuel mileage. Carbs don't do as well on gas as CIS or EFI.

[David]

I took the EFI101 class expecting to do my own tuning. The class made it seem easy, but they didn't go into all the details about making it idle smoothly and start easily when cold.

I figured, I'm a pretty smart guy, engineer, etc. As it turns out I could barely get my car to run well enough to drive it around the block. OK, I got it a little better than that, but not much better. I really wanted to do as much tuning as I could before it went to the dyno for final tuning, but it just wasn't going to happen. Fortunely, I choose my tuner first and then bought the ECU from him. So I knew when I was ready to hand the car over to a pro it was with a system he knew.

My recommendation is find a tuner (not just a mechanic) you trust and buy the system he's familiar with. I'm not too thrilled with the Electromotive stuff. They sell a bunch of them, but I've heard several stories of reliability problems.

[boxermania]

Every system has it's pro's and con's. On any given day carbs will make more HP than EFI. However tunning carbs, consumption and cold starting can drive you crazy.

EFI, also has it's quirks, however, if set up right it ca give you driveability, management and easy starts bar none.

Not knowing anything about your system I would say of the top of my head, based on the A/F ratio at idle that your injectors are sized too large. Typical ECU's have about 1.5 sec cycle time (on/off) at idle, anything less than that afects the repeatibility of the injector. I need to qualify the above on the basis that all other engine parameters are OK.

Check the number on your injector, typically Bosch and crossreference the #s per hour delivery. Run of the mill SC's are in the 24 #/hr to 30 #/hr range good for a 240 to 290 CHP.

It is imperative that one fully understands the FI theory, before attempting to tune a system. Is it doable, of course it is and when you finish it also provides a lot of satisfaction.

Let us know how you make out.....good luck.

[rfuerst911sc]

My injectors were described when I bought them as 30 lb. per hour high impedance.

[TimT]

30#injectors are to big.

figure 200hp @ 0.5 BSFC, 80% duty cycle

the result is 20# injectors

Even at minimal injector dwell time the 30# injectors are flowing to much fuel, as indicated by the 10.1 afr

Once you install properly sized injectors, Ill bet the tuning will go much easier

[rfuerst911sc]

TimT I agree and I had talked with the folks I purchased the "kit" from about injector size as originally they were going to sell me 23 lb. but they couldn't get them so they gave me 30. I really believe after all I've done that this has to be it. I have sent a email to the vendor asking them to supply smaller injectors so I can try them. I'll let you know.

[irnwill]

What's your fuel pressure? The TBITZ EFI kit uses 30lb injectors but they are run at 2.5 bar fuel pressure insted of the normal
3 bar.

[Jeff Alton]

I picked a tuner first as well, and then bought the ECU from him. I will be firing up my 3.4 in late feb or early march so I will see if this was the correct approach. The tuner feels confident that he can tune it pretty easily and I have driven some of his other non Porsche cars and they were impressive. Time will tell!

Cheers

[rfuerst911sc]

I am running 40 lbs. fuel pressure at idle. I do have a adjustable fuel pressure regulator. Is 2.5 bar 25 lbs.?

[LakeCleElum]

Originally posted by rfuerst911sc
I am running 40 lbs. fuel pressure at idle. I do have a adjustable fuel pressure regulator. Is 2.5 bar 25 lbs.?

1 bar = 14.7 lbs...

[jmshepard]

I will be a nattering nabob of negativity concerning the Megasquirt.
I gave up on the MS in my 911SC after 1+ year and a lot of "upgrades" (WB sensor, MSII) in an attempt to make it run decent in all conditions. I found that everyone I spoke to regarding MS drivability would say, "It’s great except for_______ (fill in the blank). The final straw was my drive across the State to a MS expert who was going to help me tune the system. I broke down on road and had several hours to contemplate the future while I waited for the tow. Although I do all the work on my 993 and SC, I came to the conclusion that no matter how bad the CIS or carbs worked, there was expertise everywhere to help with those systems. The MS system is a boutique item that is difficult to find someone with experience close at hand. I just bought a set of carbs for my car. The amount of money I spent on the MS and the carbs could have covered a set of PMOs. RarlyL8 is on target.
Jim S.

[rfuerst911sc]

jmshepard I hear you loud and clear. I'm close to folding the tent and going in a different direction but not giving up yet. I'm going to try smaller injectors and see what that does, if that's not the answer plan B will be carbs.

[TimT]

I think it would be silly to give up on EFI now....Once you have the correct injectors and can tame the idle, the rest is easy..

What will a set of PMOs set you back? $2600 or something?

Even if you give up on MS you could get another "name brand" ECU for around $1200 or so, and wire it to all the sensors you already have in place. You have made a substantial investment already for the TWM throttle bodies, and necessary sensors, it seems counterproductive to give up in that investment.

Usually the most difficult part of installing EFI is getting the engine to run... at all!! We do EFI install on all makes..Mazdas and Hondas are a pia especially if the customer wants a stealth install where all existing sensors are used.

Since you have a engine that runs you are already ahead!! now its a matter of tuning. Tune all the sites at no load.. then progress to the load sites.

If your supplier cant get you 22# injectors try Marren , we buy our injectors from them, $30 each for blueprinted 22# injectors.

[boxermania]

rfuerst911sc

Tim T is correct, actually most injectors output are rated at a supply fuel pressure of about 41.5 pounds, interestingly enough this is a number that has not been universally accepted.

Nevertheless one of the most nexpensive things that can be done is reducing the supply pressure via a pressure regulator, the nice thing is the the stock electric pump puts a hell of a lot more pressure han you need and there is also a return line to the tank....so an adjustable FPR with a return port will be another way to help you in tunning the EFI.

One of the telltale signs of too large injectors is that the car will load up at idle....jut as I mentioned in the earlier post and like you are experiencing.

The CIS, although a great system when tuned correctly, highly complex, but limted in performance is a prime candidate for an EFI update. With aditional HP to be gained.....more so if the pistons are upgraded as well as the cams, which is somewhat limited in a CIS motor.

Don't give up just yet.......if you can't get satisfaction with the vendor I believe that I have a set of Bosch 19#s and also 24#s laying around from my prior toy and will gladly loan them to you to test. Need to look for them......hmmmm

BTW, RC Engineering also supplies injectors and injector service, matching, etc.

[mb911]

man where the heck did you get the kit from.. This has been going for along time and I thought you had it worked out.. My kit from tony uses 30lb injectors with 3 bar of FP but I am turbo charged now..

question If I recall I believe the MS vacum line needs to be on a specific side of the throttle plate or you get full rich at idle..

I do like My MS its cheap and pretty easy for me to change Ve's to get me the correct AFR's

If I were you I would not quite but maybe if the injectors don't work out switch ECU to something else that will be esier to fond someone to tune. No way would I go carbs

[Richard Burns]

I've got TBITZs' EFI on my ROW 77 Carrera and I had a few problems getting it sorted. Each time I started the car to check it the settings were all over the place. After a lot of swearing and so forth my auto elec. suggested that I may be getting electrical interference and suggested I fit a gadget that is used to stop this sort of thing for radios etc. We did that and then tuned the car this was December 14th the car has not missed a beat since and the tune is still at the settings that we set then.
The only problem I have now is flooding if I stall. Tony of TBITZ has asked me to send him a configuration file so that he can find out why this is happening. When I find out how to get this file it will be emailed to him.
BTW when it was dyno'd I had picked up 12 kw at the rear wheels over the CIS system.
Keep trying I am sure that you will get to the problem. I would read and reread the tuning guide that you can download from MS as there is an adjustment where if you set it lower than a particular point instead of reducing your fuel you actually double it. I will try to find the section and get back to you about it.
Regards,
Richard.

[rfuerst911sc]

I received an email late yesterday from the vendor of the kit and he is sending out some Boxster 21 lb. injectors today. Hopefully I will see positive results from those. I don't want to give up on EFI because I believe it is a superior overall fuel delivery system but screwing around for a year now has mentally worn me down. Thanks everyone for the suggestions I really appreciate it.

[beepbeep]

First of all, EFI ECU is just a computer. It's the software that counts. You cannot just slap on smaller/bigger injectors and expect it to start working OK.

Car must be mapped in usual manner in order to function correctly. Blaming the ECU for rich idle is like blaming the HP computer for spelling errors you did in Word.

If you don't havve the means or the knowledge to map it yourself then you picked up wrong system.


As you do have WBO2 logger, I suggest you to swap to smaller injectors and give it a go again. Use conservative ignition map and make sure your lambda values are:

1. 0.8 when accellerating at WOT
2. 1.0 while steady-state
3. Fuel-cut when doing engine braking

If you bring your fueling to above levels, motor will run quite well as long as mechanicals are sound. When that is achieved, you can fiddle with ignition maps to extract maximum BMEP and torque.

In order to do the things above you must make sure that following points are achieved:

1. Motor is mechanically solid, no vacuum leaks, cams are correctly adjusted etc.
2. TPS works and repports correct values to MS
3. Data link between MS and lamptop works and you are able to change/alter fueling maps
4. Injectors aren't clodged and fuel pressure is OK

EFI is as reliable as bucket of rocks, once you understand how it works. It isn't a mechanical system and thus cannot be "tuned" by just changing the parts. Make sure you understand the workings and to the troubleshooting in methodical way.

I suggest following procedure:

1. Install new 21 lb injectors. Make sure fuel pressure is OK. Check injector impedance (low/high ohm?)
2. Check engine for vakuum leaks. Check that MAP is rapporting correct values to ECU (should be between ~0.3 to 1 bar absolute pressure) You are using ITB's, are you sure you aren't getting pulsating MAP signal? If you do, make a small pressure vessel and connect vakuum hoses from each runner into it to smooth the signal.
3. Connect your WBO2.
4. Start the engine and make sure your idle lambda is 1.0. If car stumbles or missfires, adjust maps until you get it to lambda 1.0
5. Do a couple of gentle runs (non-full throttle) and log lambda, MAP and RPM values. Read the values from the logger and correct ECU maps accordingly until you hit lambda 1.0 troughout the range on half throttle.
6. Extrapolate fueling values at presumed full-throttle and add some extra margins (so it runs rich). Do a couple of pulls at WOT, increase/decrease the fueling until you hit approx. lambda 0.8.
7. Fiddle with cold-start enrichment until car starts w/o problems when cold.

Once you are done, you should have fairly well-running engine. You can extract some extra horsepower by optimizing the ignition timing in case you havve MS fuel & spark installed.


Just be methodical. EFI is very very good thing and is miles better than CIS. People that say EFI is overrated usually don't quite understand how it works and are scared by presumed complexity. EFI is not overly complex, but it's complexity lies in other domain (electronics vs. mechanics). If you have problems with grasping the fundamentals of electronics, you will have a hard time finishing such project and are better off leaving it to pro's. On the other hand, it is highly rewarding to do it yourself and you will both save you money and learn a thing or two.

Good luck!

[914efi]

I did an SDS system on a 2.2 E engine about 5 years ago (when their 6cyl crankfire became available). Needless to say, I learned a lot. I jumped with both feet doing the ignition, injection and making my own manifold.

The biggest thing I learned is that nobody really understands this stuff outside of the people on boards like this that have actually done things like this. You need to think hard and really understand what the system is trying to do. If there are interference issues, that is much harder to self detect.

The smaller injectors are probably a good move, I used 3.2 carrera units on my 2.2, and I ended up reducing the fuel pressure to try to make low speed driveability better. Do you have aTPS? The Bitz system does not, and this can lead to some trouble particularly if the engine is modded away from standard. A basic SC should be amenable to EFI with few problems, so stick with it. I would have advised keeping the stock manifold, but it should be workable with the ITB setup. As you mention, the vacuum signals can be tricky. A restrictor into a cannister of some type should be good. Do you monitor vacuum to see what it is doing?

If you think you are having interference issues, some properly placed filters will help that. This was my weak point, I am not an electronics person, but a few questions here or on the MS site should help you. Check the SDS site, there is a lot of really good info there. You are in somewhat uncharted waters, so your thinking cap needs to firmly in place at all times.