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Some observations from my recent turbo swap (LH2.4 stuff)

Captain Bondo

Exklusiv Zubehör Klub
300+ Club
Sep 18, 2002
At work this week I put a B230ft from a '93 940T into a '90 245, did the shakedown runs today and so I just thought I'd make a little almost mental note for posterity's sake on the process.

Basically, the 940 ignition and fuel computers were swapped.
The injector ballast resistor pack located at the front intake side corner of the engine bay was cut WITH plug (you want the plug) form the 940 harness.

The injector ballast was spliced into the thick green/white wire by cutting the wire approx 2" back from the plug for the fuel computer- this allows you to mount the ballast cleanly inside the kick panel. Basically tie the four green wires on the plug together and solder them to one end of the snipped green/white wire, and solder the grey wire to the other side. soldering the plug in rather than the ballast itself is important for two reasons:
A)if you pull the motor with harness, you can unplug the ballast resistor inside the car and not have to squeeze it through the hole in the firewall risking damaging it and,
B)if it burns out you can replace it easily because it isn't hardwired.

The 940 fuel rail was also swapped wiht its green injectors. The rail has no provision for the cold start injector, so you can either not run the cold start injector or swap the green injectors into the original fuel rail. I left the cold start injector disconnected- my reasoning being that the cold start mapping for the turbo computer assumes there is no cold start injector.

So, basically I swapped the computer, injectors, and ballast in and then ran the car as-is. This confirmed that everything would work as-is without throwing any codes.
As an aside, the 940T was equipped with EGR, the 90 245 was not. I canned the egr and it doesn't seem to throw any codes.

Completing that, I pulled the drivetrain form the 240 with harness.

Next I pulled the drivetrain from the 940 without harness (motor harness is integral to the chassis anyways)

I removed the intake, started, and alternator from the 240NA motor all together
and bolted it all to the 940 motor.

I removed the intermediate shaft from the 240 and swapped it into the 940.
The 940 motor got obligatory t-belt/seals/rear main seal/waterpump at this stage.

So now the 940 motor has the modified 240 harness on it with the block mount dizzy.

Transfer motor mounts and heater hoses.
Back into the car, hook everything up, installed the 940 T downpipe.
The downpipe just BARELY clears the firewall, it does hit under end torque/vibration. Solution is to heat it up near the turbo flange and tweak it a little.

I extended the AMM wires so that they run across the lower rad support and around to where the windsheild squirter motors are and installed the AMM there with a short pipe just fabricated on the fly from another intercooler pipe. Use an IC pipe that has a nipple for the idle speed motor, as you can use it to plumb the breather with the appropriate hose bought from the dealer- this way the pcv will work as intended with the box seeing vaccuum as generated by the turbo inlet.

This was a quite straightforward conversion and it goes pretty good for a nice stock conservative setup (this ain't my car its a customer's so it had to be nice and stock and clean). Not sure how long the M47 will last though! :lol:

Anyways work is largely just plain old maintenance work and motor re&re but I figured I'd post this since it might be something someone wants info on at some stage. Would have been cool to take pics of the process but it's pretty straightforward and stopping to take pics at work might come off as a little odd.
I have heard, but not confirmed, that a non EGR motor should not be run with an EGR computer and vice versa. I recently did an EGR motor swap into a non EGR car and had only the EGR computer and retained the EGR for this reason.

Philip Bradley
Based on my understanding of the egr system, I can't really see what harm it would do. Using the original non-egr motor w/ the egr computer, I ran the car up using a 4 gas analyzer/oscilloscope and noticed no mixture readings that would suggest anything unhealthy going on. I had to test this all thoroughly as the car of course has to be capable of passing emissions without the customer having to do anything at all.
Perhaps the efi cars are different, but I know of plenty of carb and k-jet cars that have been driving around with the egr deleted for 20+ years. All it's doing is re-burning hydrocarbons in the exhaust gas, I can't see it creating a significant mapping error.

Anyways not saying its not possible but I'd like to hear the reasoning,
Ya, I was gonna axe that too.

I suppose I'm going to answer my own question here, but, the doesn't the ECU require a signal from the transmission? Or is it the other way around and that's why you can swap trannies without a problem?
Ok here are the updates:
Looked the EGR thing through. With no egr temp sensor connected to the computer, it defaults to thinking the motor is too cold to operate the egr, so it simply does not operate the solenoid and operates normally. So no issues with that, just so everyone knows.

LH2.4 has no transmission signal, the 940t had an AW71, the 240 had a M47, so I just swapped the m47 stuff over since the flywheel was already setup for the crank sensor. You just make sure the 2 dowels on the back of the flywheel are at 2:00 and 3:30 when you bolt it on with the motor at TDC so that the crank sensor signal is in sync, and you're good to go.

How long did it take me? Total actual labour time including pulling both motors, testing all of the ecus to make sure it'll pass aircare, plus swapping the int shaft, replacing t-belt, waterpump, front seals, rear main, breather box service and o-ring, swapping the trans over, and reinstalling the motor and modifying the harness it was about 12 hours.
I can do a straight motor swap in about 4 hours or so, but the fiddling around making sure evrything was just so ate some time up. now that I know all of the electronics works I could do it in maybe 10 hours.

I think the customer is picking it up either today or saturday, so I'll take note of what the bill ends up being, that will sorta be up to my boss.


Oh, another interesting thing, the little sheetmetal clip that you clip onto the fuel pump relay, and then clip to sheetmetal up inside the dash, clips right onto the ballast resistor so you can grab another one of those clips you can clip it up right beside the fuel pump relay, it looks factory.
Thanks for researching the EGR/computer issue. A Volvo mechanic suggested to me that the computer might have a different fuel curve for the EGR fed engine since the EGR gas is post AMM. I decided to play it safe, and retained the EGR and EGR computer.

For a follow up question, do you think EGR helps or hurts performance or makes no difference? I could add EGR removal on the daily driver to my long list of car projects or I could just wait until the day an EGR fault code appears and then remove it. I was trying to keep the car stock, but some browntops found their way into the fuel rail and a G Valve into the wastegate signal line and a used IPD/TME 2.5 inch exhaust onto the downpipe . . . .

Philip Bradley
That is a good question, I am not sure it hurts that much, but at the same time it can't help that much either. Recirculaing exhaust gasses can't help performance. When we put my bro's 95 motor in his 765 I didn't use it. I would like to find out more info on this though.
I would say that honestly you won't see a major performance difference either way. The major idea behind it is that as you come on throttle you get that nasty lean spot the LH cars amonst others are so famous for (part of why even a mild 2.4 car will often ping once or twince on throttle opening). The nasty lean spot coupled with an increase in load means that you get a spike of hydrocarbons which the emissions police don't like- it is under these circumstances that the egr valve really takes effect to re-cycle the hydrocarbons back through the engine to re-burn them.

One could argue then that allowing exhaust into the motor acts like decreasing the VE because exhaust gas has a low oxygen content and the volume that the recirculated exhaust takes up in the chamber could have been fresh air. This suggests less power but I think in reality it's pretty minor. If it is functioning correctly I'd probably just leave it alone, but if it failed I would not hesitate to remove it. On the older cars the valve likes to stick open which tends to lean the car out since it still sucks unmetered air into the intake even if the "air" is exhaust gas and is somewhat oxygen depleted.

I just flogged the car up to the exhaust shop with the open 940 downpipe clanging away. :lol: The downpipe will be modified and a stock 200 style turbo rear exhaust kit fitted. Customer is supposed to pick it up tonight so I'll have some price numbers tonight-ish.
It was a fun project overall and it's a neat daily driver.
Nice right up. One question I have is does the turbo computer need any additional sensor inputs that the NA doesn't? I thought and could be wrong that overboost was an input to the ECU. I don't think the cold start injector matters either way. Supposedly only comes on at
-20F and was mostly elminated on later cars.
Yes, one thing worth mentioning is that the car has no provisions for overboost. :)

oh also labour costs for the swap ended up at CAD $1300+parts
overboost/fuel cut on a LH 2.4 car is controlled via the voltage @ the AMM ... or well the ECU so as long as the AMM is hooked up the 'overboost/fuel cut' switch is hooked up

and as far as the EGR and non EGR 2.4 setups from swaping 560(egr w/ cold start injector) and 563 ECU's (no egr but cold start) i found the 563 did run a fair amount richer in the mid range tho it did seem a little more sluggish(on a egr equipted car) ... tho from a local volvo tech i was told that was because the 560 ecu might have a bit more timing , so that's what i'm told so i have no idea, tho most all of those damn 2.4 parts can be swaped w/o any issues
True on the AMM, but I think there is still an overboost switch that cuts power to the fuel pump relay though which I did not install. I'll check. I didn't look into it carefully as I've always sorta seen them as a bit of a farce. ;-)

I'm not sure that there is a timing diff between the two computers as I think it is EZK that determines that, although one thing I do not know much about is how EZK and LH "talk" to each other.
Captain Bondo said:
True on the AMM, but I think there is still an overboost switch that cuts power to the fuel pump relay though which I did not install. I'll check. I didn't look into it carefully as I've always sorta seen them as a bit of a farce. ;-)
nope LH 2.4's only form of overboost is from air flow over that AMM wire 5.1V or around there. if you ever do hit it you can just do what the dodge guys do(and what i did) and install a zenir diode to keep it from seeing that voltage, just make sure you have enough fuel and octane for all of that extra pressure(its not smart but for now and on a full tank of 100oct it works fine upto 20psi)

I'm not sure that there is a timing diff between the two computers as I think it is EZK that determines that, although one thing I do not know much about is how EZK and LH "talk" to each other.

i used to know what all LH told EZk so i'll look it back up tho yea i figured EZK was timing but from what i think they were telling me is that EZK reads the sensors and LH does all the work and has the maps in it tho that doesn't make sense because then y would u need the turbo ezk box so hm .. i'll try to see if i can dig up my old lh 2.4 convo's
I'll guess that if certain airflow levels show up in certain low rpm ranges, timing is pulled. I don't think there is a fixed timing curve that relies solely on the knock sensor, but I could be wrong. If I am right, though, there is a drawback to the voltage clamp -- the timing won't be adjusted lower and only the knock sensor will be available to help reduce timing to accomodate the higher boost.

I am not done tuning my 93 945T with LH 2.4, but it seems to have more of a transitional ignition ping than my 88 745T with LH 2.2 when you go into boost hard. I'd rather not hear any ping.

Philip Bradley
pbonsalb said:
I am not done tuning my 93 945T with LH 2.4, but it seems to have more of a transitional ignition ping than my 88 745T with LH 2.2 when you go into boost hard. I'd rather not hear any ping.

that's kind of an issue w/ 2.4 as most everyones cars do that and i don't thinkwe have figured out why yet(some say 2.4 has more aggressive timing maps vs 2.2)

the voltage clamp is a horrible idea but for me it works because i only use it w/ pure race gas so as stupid as it is the race gas helps me keep a little safe. w/ the knocksense i usually get the light to come on around 5200rpm almost no matter what psi i'm running but i have heard knock above that rpm range before on pump gas(way back when) and its always been just one or two light nothing big or major. w/ the 100oct i have yet to hear any knock @20psi all the way up to 6200(when my tranny was going it wouldn't shift so i bounced it off the limiter a few times

i really wish i had the smt6 that E.S. had on his car so i could see what 2.4 is doing w/ the whole clamp tho i'm pretty sure i remember him telling me that after all of the research he's done about 2.4 that after around 4200 rpm 2.4 has pulled all of the timing that it will out of the engine and any more timing it pulls is via the knock sensor(so i run 100oct and the motor a little on the rich side to be safe, its not for the best power but its working so far) as i do plan on hitting those major 13's for less than 1k in 'mods' so as soon as i've done that(and kenny sends me my MS kit) i'll give up on this crazy idea tho the fact is it does work as long as you can keep enough fuel in the motor
motor swap

Great writeup Kenny! I have a 89 244DL that has 2.4 and was wondering if a turbo 2.4 motor was a viable swap. It's also an M47 car. I believe there is a load signal that connects the
LH2.4 ecu and the EZk ecu. Isn't that used to pull the timing when under boost?

Enjoy the road,
Great thread!

What did you do with the crankcase ventilation? There's som sort of sensor on the turbo models that's not found on NA
U.N.C.L.E. said:
Great thread!

What did you do with the crankcase ventilation? There's som sort of sensor on the turbo models that's not found on NA

there is?

i know NA models have a flame trap inside their PCV valve, while the turbos do not and have the port capped off
I'll post what little I know about LH2.4, EZK and EGR at least on Saabs. I joined here 'cause you guys are pushing the envelope a bit more that some of the Saab groups. I have a '91 900T with EGR. Apparently, Saab had enough of a problem with these that they had a Cali recall on all 90 and 91 900s with EGR to replace the ECU, pull the EGR. The replacement was the '92-93 unit. I cannot remember the Bosch number. I swapped out the ECU (582) and pulled the EGR stuff (just like the recall). It runs better (more power) and a nip cooler on the temp gage. I would agree that it has a different fuel map, it sure does feel like it. I have conversed with 2 other guys with these ECUs and they note that the ECU will set a CE light, but a resistor across the temp sensor leads kills it. I do not know about this as I have never tried it. It does make sense to me, though. Good idea to measure the hot resistance on the EGR temp sensor and put in a resistor with that value. I think the value I have read is 10k, but do not know. As far as communication between EZK and LH 2.4, I thint is a load signal from the LH to the EZK which tells it how hard it is running. We do not have EZK on our Saab Turbos (only NA cars), so I have not really paid much attention beyond that. I will not be using this ECU for anything other than a case donor for MegaSquirt, though...