88 89 ecu vs 87 ??

[sittin-sideways]

ok i got 87, i just want to know how better will my car run with a88 or 89 ecu.

and is 88 better then a 89 or no diffents.

 

thank .

 

p.s. will ecu from 88 89 auto starion work on 5spd starion

Edited June 3, 2008 by sittin-sideways

[Skippy]

Yes it will work and if you do a quick search you will find the benefits. I don't know them off the top of my head or I would tell you, but I do know you can find all this in the search.

[mikec]

The 88-later ECUs are designed to function with higher boost levels than the earlier ECUs. If you use a manual boost controller (MBC) or electronic boost controller (EBC) to increase your boost levels, you'll eventually reach some value that "confuses" the ECU. That upper value is not too high on 87 ECUs; it is generally MUCH higher on the 88-later ECUs. So folks that want to "crank up the boost" often have to swap 88-later ECUs into their 87 cars.

 

Just changing the ECU though will NOT change the boost pressure - that's controlled by the mechanical wastegate system. All the ECU swap does is give you an ECU that "understands" above stock boost levels before going stupid.

 

Some folks feel the 88-later ECUs have better air:fuel maps too; that you'll see a gas mileage improvement. I didn't. In fact, a relative's 87 that I work on recently got an 88 ECU installed since the 87 one seemed to be dying. MPG went down slightly. Driveability didn't seem to change; and the air:fuel guage still hunts properly. If the car runs fine on the 87 ECU, and you don't plan on cranking up the boost, don't bother with swapping the ECUs... you won't see any "oh wow" improvements.

 

87-later ECUs don't care what tranny you have in the car; they work fine with both autos and 5-speeds. The earlier cars though have different ECUs depending on tranny type. And the 87-later ECUs have different pinouts/different pin counts from earlier model years. In fact, I don't think you can do any ECU swaps on the early model year cars without some re-wiring; you can't simply stick an 85 ECU into an 84 for example.

 

mike c.

[sittin-sideways]

The 88-later ECUs are designed to function with higher boost levels than the earlier ECUs. If you use a manual boost controller (MBC) or electronic boost controller (EBC) to increase your boost levels, you'll eventually reach some value that "confuses" the ECU. That upper value is not too high on 87 ECUs; it is generally MUCH higher on the 88-later ECUs. So folks that want to "crank up the boost" often have to swap 88-later ECUs into their 87 cars.

 

Just changing the ECU though will NOT change the boost pressure - that's controlled by the mechanical wastegate system. All the ECU swap does is give you an ECU that "understands" above stock boost levels before going stupid.

 

Some folks feel the 88-later ECUs have better air:fuel maps too; that you'll see a gas mileage improvement. I didn't. In fact, a relative's 87 that I work on recently got an 88 ECU installed since the 87 one seemed to be dying. MPG went down slightly. Driveability didn't seem to change; and the air:fuel guage still hunts properly. If the car runs fine on the 87 ECU, and you don't plan on cranking up the boost, don't bother with swapping the ECUs... you won't see any "oh wow" improvements.

 

87-later ECUs don't care what tranny you have in the car; they work fine with both autos and 5-speeds. The earlier cars though have different ECUs depending on tranny type. And the 87-later ECUs have different pinouts/different pin counts from earlier model years. In fact, I don't think you can do any ECU swaps on the early model year cars without some re-wiring; you can't simply stick an 85 ECU into an 84 for example.

 

mike c.

ohok cool

so just better off with mbc.

[Skippy]

ohok cool

so just better off with mbc.

 

The 88 and 89 had 11 more HP stock then an 87 (188 compared to 177). If memory serves me right it was because the 88 and 89 had a more efficient Intercooler (cooled air more and flowed better) and better fuel management system. That fuel management system could be other things in addition to the ECU, but I had always heard that was part of it. However, the single biggest reason to change to is is because of what he said above. It removes the low boost cutoff that non88 and 89 ECU's had allowing you to boost more.

[Caliber308]

The only difference i've heard of is the fuel cut on a 88/89 is higher than a 87. Who knows?? I have boosted my 1987 ECU over 15 psi. And have heard the cut off is 14.5 on the 87 ECU???? It couldn't hurt. I'm running a 89 ECU with no fuel cut. But i'm also running a Walbro, Larger fuel injectors, Aeromotive FPR and a MAF-T set up.

 

CALIBER 308

Edited June 5, 2008 by Caliber308

[JAinsworth]

I don't think there is a boost related fuel cut on the 88/89 ecu, if so its above 25 psi.

Jimmy

[JustPaus_88TSi]

~sigh~

 

There is no such thing as fuel cut in these cars. At least 87-89's.. I have no experience with 83-86's..

 

 

Say it with me now...

 

MAS Overrun. Fuel might be being "cut", but it has nothing to do with the ECU other than its decision to say "I don't know what to do, so lets not do anything at all until I can read a clear signal from the MAS".

 

 

Like Mike was saying, Mitsu supposedly kept working on the fuel maps each year. I'm sure the difference is negligable at best though.

 

Want a higher usable boost range if you're ready for it? Upgrade(1G MAS, GM MAF-T) or eliminate(megasquirt or other MAP based system) the MAS, or get a SAFC, Emanage or AEM FI/C.. Or both the MAF-T and a SAFC or other piggyback..

[Skippy]

You will probably blow a head gasket before you can turn up enough boost to lean out the injectors. Though I personally have not nor can I confirm this but I am going to bet our stock injectors can provide plenty of fuel to these cars, probably enough for 325+HP. The below formula I found while researching the target AFR for a MAFT.

 

A very rough formula to determine the power level a injector can support is simply to divide the total flowrate of all the injectors by the BSFC (Brake Specific Fuel Consumption).

 

Being that I do not have the flow rate nor have I had my car Dyno'd so I can't get the BSFC, I am unable to do the math on it. Someone else here probably could though.

 

With that in mind I would say you are not correct in stating there is not a fuel cut. I know first hand on my 87 if I turn my boost much higher then 10 it cuts. From what I have gathered the 88 and 89 ECU the cut is in the 20's which should not be a factor for 99.9% of the people here.

[Caliber308]

Everybody should read this:

 

Starquest FAQ Forum Page 6

 

87 to 88/89 ECU upgrade by KO.

 

post no. 9 by Mike C.

 

 

CALIBER 308

[JustPaus_88TSi]

You will probably blow a head gasket before you can turn up enough boost to lean out the injectors. Though I personally have not nor can I confirm this but I am going to bet our stock injectors can provide plenty of fuel to these cars, probably enough for 325+HP. The below formula I found while researching the target AFR for a MAFT.

 

You'll be hard pressed to make more than 260rwhp on stock fuel. 325 isn't goin to happen with stock sized injectors. Even my setup with two 1050's is pretty much at it's limit at 325-330rwhp or so.

 

 

 

 

With that in mind I would say you are not correct in stating there is not a fuel cut. I know first hand on my 87 if I turn my boost much higher then 10 it cuts. From what I have gathered the 88 and 89 ECU the cut is in the 20's which should not be a factor for 99.9% of the people here.

 

~sigh again~

 

There is no such thing as fuel cut, period. The ECU doesn't go, "hey, boost is at 15psi and i'm an 87, so 'yoink', no more fuel for you".. These cars aren't smart enough, nor were they programmed to make such decisions. The closest thing you'll find to that level of sophistication is the 88-89's BCS system and it's ability to cut boost to 7.5psi in the event of knock.

 

Read my last post again. It is MAS related. Your 87 is a prime example why this has nothing to do with the ECU. 87's will usually be okay at 14psi, you MAS is old and likely not up to 100% operational condition, thus it's be able to be overran at a lower flow rate(boost level).

 

All the ECU does is deliver the spec'd amount of fuel based on it's mapping and the signals it receives from the MAS, CTS and TPS.. If the MAS sends a garbled signal to the ECU because your boost level maxes and goes beyond that of the air flow meter's ability, the ECU will get confused and not give you the fuel because the signal is crap and unreadable.

 

Want to fix it? Get rid of your stock MAS.

 

A faulty CTS causes all kind of similiar problems, so does a TPS with dead or flat spots in its range of sweep.

[Chad]

A perfect demonstration of mas over run and factoy fuel cut:

 

My 86 would fuel cut bone stock at 9.5 PSI (the accepted norm for 86's). I got a FCD and PFC F-con, oversized injectors, and electronic boost controller and ws able to consistantly run 23 PSI on my stock 12A turbo. I took out the stock 12A and mounted an adapted T04B to the same setup, nothing else changed. I was NEVER able to get more than 12 PSI out of that T-4 before the cut out occured whith the T-4.

 

Later, I converted the car over to a 1st gen mas and an 88 ECU. I also adapted the F-con to use the new ECU. I was able to get 19 PSI out of that setup.

 

It's not just the MAS, or just fuel cut, it can be both or neither, dependin go on the combination of parts.

[Skippy]

 

If you havent done the math on the injectors you are speculating on what they support. You seemed to be armed with all the information. Toss it in the forumla and let us know so we then can make an educated decision on when it is time to put larger injectors in with a control unit that will utilize them. (Seriously)

 

Being that the 87, 88, and 89 all had the same injectors and the same MAS what changed to cause this "non fuel cut" rate to be at a higher boost?

 

Maybe I am misinformed and they didnt have the same MAS and Injectors, but if they did something was causing the issue at a much lower PSI on the 87s compared to the newer years.

 

Does the 88/89 ECU have a longer spray or induce a higher fuel pressure? Those will be the only other things that will effect the amount of fuel delivery if the injectors are the same.

[Chad]

Lots of us have done the math long ago on the TBi setup.

 

http://www.rceng.com/images/rc/formula-2.gif

 

It's common knowledge that you are lucky to get more than 220HP at the rear wheels (about 260 crank HP) on stock injectors

[Chad]

those calcs show 228.8 flywheel HP for a 80% DC and BSFC of .50. You can run higher than 80% DC, but that is dangerous and can damage the injectors so you should never design a setup to run that high. Those figures are also baised on fuel pressures higher-than stock.

 

That was figured on 1500 cc min, which is the nominal flow on 87-89 injector setups (one at ~500, one at ~1000).

 

To convert cc/min to #/hr : cc/10.5 = #

[JustPaus_88TSi]

Calculators mean squat. We don't even know the total air flow numbers or VE values for this motor.

 

The 260rwhp I spoke of is a members car on stock fuel that was "breaking up" in that area, so going higher would lead to problems. Starcon88(Kurt) is the guy, made 260rwhp/360rwtq with a small 16g@20psi and went 12.9@105 or 106..

 

Indiana can explain exactly what he saw much better than I can, as he's the one with all the hands-on experience with Kurt's car.

 

 

As far as I know, nobody has been able to dissect the ECU's to see exactly how the fuel maps were "worked on" by Mitsu every year. This is pre OBD-I stuff here. I believe you are correct about the 88-89 ECU's inducing a longer spray pattern as the boost increases, because there was no deviation in base fuel pressure as far as I know(all were 36-37psi@idle).

 

 

If the 87's were designed to run 7.5psi, why would the factory create maps for more than double the boost? 87's usually have problems above 14psi, where 88-89's are usually okay at 18psi. There have been people that have gone higher with 88-89's, but they are the exceptions. There's a limit as to how much higher than stock Mitsu designed the fuel maps to accommodate, roughly 6-7psi for 87's and again about 7psi for 88-89's. It sounds like Mitsu implemented "what if" scenarios while creating the fuel maps. Demand more from a turbo that can actually flow it(like Chad's Garrett) and you'll freak the ECU out by demanding fuel for airflow that was never designed to be ran. Boost pressure means nothing to the ECU. 15psi on a 12a could very well be in the same fuel map area as a s16g@13psi, or a T04R@10psi. That's just my view of it.

 

On my old setup with stock fuel(injectors, FPR, pump), 12a and a 3" AHP/exhaust with a 1G MAS, I had no problems with 19-21psi. My issue was lifting the head on stock studs, that eventually led to me rebuilding it(after inspecting piston/ring clearances) and going to a FIP fuel system.

[Indiana]

This may be short I'm a bit induced so to speak at the moment but...it won't matter if your boost is 5 or 50 when you hit WOT based on what the TPS output is there isn't much left other than what the MAS is saying cause the 02 is useless here so is any movement of the TPS to add additional fuel for enrichment and the distributor is likely maxed out for the timing advance and the boost retard that is subtracted from that (happens about 5500rpms) and how the CTS comes into play I'm not sure. The post 86 ecus have no pressure sensors so what boost you have is not reported. You may like to hear some recent talk of how a MAS is superior to a MAP so go check that out it only makes sense but that would be like saying what a MAS and its limit is cause a MAP sensor reads only pressure it knows not a flow RATE only flow PRESSURE. A MAF or MAS knows flow RATE only so ah if you have enough wind passing through a door to blow up the roof on a football stadium in a minute don't you think it could report back a different signal if it was only enough to blow up a small balloon? The PRESSURE put back into the intake is about what size your turbo is, its efficiency, its HEAT level and the intercooler and how it performs then and only then does that air go into the intake. Can an ECU read both a MAS and MAP signal? that's what they attempted to do with the 86 ecu then they gave up and went with the 87 style. If you have an 87 and can only run 10psu then you have a major issue with something else its not a boost pressure limit that is for sure. If you can't get past 25psi on an 88/89 ecu you also have other issues. What's the point of this again? Ok, you got two injectors and they are stuck in a hole and you have some formula that says you can get 350hp. GREAT, what else needs to be done? cause its too bad the stock ecu has its limits on how quick, how long etc of what it can do to fire those injectors and that my friend IS THE LIMIT and it has NOTHING to do with boost pressure. An injector can only fire so much sure but what is making that happen is an antique don't expect to much from it. What you can do is increase the fuel pressure to those injectors and that is really all you can do. If the MAS has an over-run I've not seen it. I can see that X volume of air passing over the MAS could create some turbulence that would effectively cause the signal to degrade, or LOWER and that may cause the lean condition but you are back to what size turbo you have and what cfms that compressor wheel needs. Will a stock system make 325rwhp I do not know but if you believe in those readings that some devices have one said, its a blitz i-d dual EBC, it said 559hp on the power meter for the peak power and that was at 30psi on an 89ecu with a big16G but at that point the fuel pressure was up to 66psi and there was some additional fuel being sprayed from a cold start valve. If you expect to get even 260hp out of the ecu at STOCK fuel pressure levels you are smokin crack.

 

What you need to do is go back and address what it was that felt like this fuel cut and I'll bet you it was NOT that at all it was something else just causing the car to seem like it was exhibiting fuel cut like the wrong gap on your plugs, the wrong octane fuel, too much total timing, too hot of air charge into the intake, knock sensor etc many things will cause what may seem like a fuel cut. What you would have to do to test your theory is get a motor and replace ALL the sensors with some type or variable output drivers that you can control with a knob and then see what happens for the "limit" of one when all others are in range. This isn't ever going to happen. We got the 261rwhp from a car with a heat soaked intercooler and all we had was an aftermarket regulator and boost of around 18-19psi. The compression ratio you start with on your motor is also going to be a part of that power equation for this rwhp you are expecting.

[1fly86TSi]

would it be possible that mitsu programmed the computers to give the vehicle "fuel cut" when the MAS reaches a certain variable reading as a safety to the engine precuation? that seems rather feesibleto me, of course, if you exceed the limit variable for the fuel cut, the computer would be forced to come up with the best it could for proper fuel mapping.

 

BTW..i got the 86 puter...haven't ever tested limits, and don't want to.

[Indiana]

A MAS will flow X cfms but that is based off what the compressor wheel size is that draws that air in

[importwarrior]

i have been running a 89 auto ECU in my 87 5 speed for 7 years no problems. Edited June 11, 2008 by importwarrior