M998 turbo conversion

[Mogman]

That sounds awesome especially with the 6 spd. I have the BMI turbo and a 700r4 and the kit had me turn it up 3/8 of a turn from stock. If in OD and bogging under a load it throws a little smoke but otherwise super clean running. Max egts so far were 900 at 12psi boost and it was ripping up a hill with 4000lbs of loaded trailer and 4 passengers and gear. I try to use the accelerator to keep it under 10 psi and plan to adjust the waste gate down to 10 from 12 psi. I’ve loved it so far and the vast majority of the time egts are 400-700. It takes a lot to make it get up to the 850-900 range.

I have a feeling from my seat dyno the turbo adds more than 30hp. On hills with the trailer I was lucky to hold 35-40 mph. Now I’m holding 55 easy and getting on the highway is a totally different experience.

I’m looking forward to seeing your experience especially with extra gears.

Where is your EGT probe located?

 

[MattNC]

Where is your EGT probe located?

A few inches before the exhaust goes into the turbo and after both sides exhaust flows have merged.

 

[Mogman]

A few inches before the exhaust goes into the turbo and after both sides exhaust flows have merged.

That would explain the cool temps, there is no doubt a difference from inside the exhaust manifold to the turbo inlet, that is where I am also putting my probe, I am going to do some research and see if I can get an idea how much (offset) one would expect to see. I am suspecting up to 200 degrees..

 

[MattNC]

That would explain the cool temps, there is no doubt a difference from inside the exhaust manifold to the turbo inlet, that is where I am also putting my probe, I am going to do some research and see if I can get an idea how much (offset) one would expect to see. I am suspecting up to 200 degrees..

i neglected to take a picture when installing but here’s a picture from BMI. The drivers side exhaust comes via a crossover and mates up on the left. You can see the passenger side ports on this manifold. The upturn to the right is where the turbo mounts. Where the arrow is pointing is where the probe is, a few inches before the turn up to the turbo.

 

[Mogman]

I went on a 125 mile shakedown run this morning, I do have a few minor issues.
One is the thermostatic fan switch is set too low, it is bucking heads with the thermostat, at 70 and above the fan comes on at 200 indicated then drops quickly to around 195 and just sits there as the thermostat maintains temp and the fan just runs, not doing much for my mileage although turning 2300RPM at 75MPH is much less distracting than the old 2900RPM at 60MPH.

The 6L80's adaptive programming started to settle down the shift points, now it is time to try and load a Cadillac 6L tune and get the manual shifting to work, I am going to consult with EFILive first about my concerns.

The oil pressure indicated 45PSI at 2300 RPM hot and around 30 at idle hot, wish I had thought about installing a HP oil pump when I replaced the oil pan, but this will be fine, one reason many of these run lower than average oil pressure is when they developed the 6.5L they added jets in the crankcase to oil cool the pistons but there is a limit to the torque that can be delivered to the oil pump with the small cam gear and 5/16 hex shaft driving the pump.

 

[Mullaney]

I went on a 125 mile shakedown run this morning, I do have a few minor issues.
One is the thermostatic fan switch is set too low, it is bucking heads with the thermostat, at 70 and above the fan comes on at 200 indicated then drops quickly to around 195 and just sits there as the thermostat maintains temp and the fan just runs, not doing much for my mileage although turning 2300RPM at 75MPH is much less distracting than the old 2900RPM at 60MPH.

The 6L80's adaptive programming started to settle down the shift points, now it is time to try and load a Cadillac 6L tune and get the manual shifting to work, I am going to consult with EFILive first about my concerns.

The oil pressure indicated 45PSI at 2300 RPM hot and around 30 at idle hot, wish I had thought about installing a HP oil pump when I replaced the oil pan, but this will be fine, one reason many of these run lower than average oil pressure is when they developed the 6.5L they added jets in the crankcase to oil cool the pistons but there is a limit to the torque that can be delivered to the oil pump with the small cam gear and 5/16 hex shaft driving the pump.
View attachment 866337

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I really like that helmet top.
Just looks useful decked out that way...

Glad you are making good progress on the small fixes after your install.

 

[Mogman]

I have two spare fan switches so I took them and hung them in a pot of water and heated them up until they both opened (fan on) then removed the heat and the one that closed first (fan off) was installed. do not tell the WIFE, she takes a dim view of me using her pots for automotive testing!!
They were both pretty close to each other, did not test the one in the truck just changed it, I have to go and get inspected tomorrow as both of my M998s plates expired yesterday so I will get a chance to test my theory.

 

[Mogman]

BTW the difference in power is now becoming much more apparent.
At first you are concerned with other "things" like "this sounds different" and watching every little "tic" on every gauge.
She does sound different though... but we sailed along no sweat both ways at 70+ where legal.
Tomorrow a 20 MPH headwind is forecast on my way home from Beeville so that will be a good test.

 

[Mogman]

Well the fan is running much closer to "normal" with the new switch.
The turbo diesel was supposed to be much more efficient than the NA but with the exception of a little more power it seems to be much more efficient at converting more fuel into more heat, this dang thing is thirsty, yes at the same speed I am using less throttle but much more fuel than before...

 

[MattNC]

Well the fan is running much closer to "normal" with the new switch.
The turbo diesel was supposed to be much more efficient than the NA but with the exception of a little more power it seems to be much more efficient at converting more fuel into more heat, this dang thing is thirsty, yes at the same speed I am using less throttle but much more fuel than before...

Any idea of the EGTs and boost? Any indications its over-fueled? I know my turbo is very different but I experienced the opposite so far. My operating temps have come down and the fan comes on much less frequently. Much of it is likely the overdrive transmission but even when I drive out of overdrive it seems better than before on not kicking the fan on as much. I've had days driving in the 60s and 70s where the fan never came on at all. Pulling my trailer on a day in the low 80s the fan only came on with long hills. I need to check my mileage with just the truck, but pulling the ~4000lb trailer for a 200 mile round trip I got 12.5 mpg which seems pretty much what I used to get without the trailer pre-turbo install.

 

[Mogman]

As far as OD I am running a 6L80 with double overdrive, I am only turning 2400RPM at 75MHP should be right up the turbos alley.
I cannot find the dang EGT meter I bought so I have another and a boost meter coming, I did have the presents to drill and tap the turbo cross over even though I did not intend to install a boost meter, I will just hook it up temp.
The GEP seems a little more "chatty" than the 6.2L maybe a timing issue.
I may also have some issue with the NA muffler plugging things up somewhat, going to town tomorrow to get a muffler delete.
Also that helmet top is like pulling an open parachute but the comparisons should have the same results as you but I am seeing anything but at this point.
EDIT, I do not think it is over fueled, I can see no smoke, this engine came out of Eastern Metals where they had a demil order on over 100 nearly new (most had less than 100 miles) ECV trucks so I am pretty sure it is bone stock.

 

[MattNC]

As far as OD I am running a 6L80 with double overdrive, I am only turning 2400RPM at 75MHP should be right up the turbos alley.
I cannot find the dang EGT meter I bought so I have another and a boost meter coming, I did have the presents to drill and tap the turbo cross over even though I did not intend to install a boost meter, I will just hook it up temp.
The GEP seems a little more "chatty" than the 6.2L maybe a timing issue.
I may also have some issue with the NA muffler plugging things up somewhat, going to town tomorrow to get a muffler delete.
Also that helmet top is like pulling an open parachute but the comparisons should have the same results as you but I am seeing anything but at this point.
EDIT, I do not think it is over fueled, I can see no smoke, this engine came out of Eastern Metals where they had a demil order on over 100 nearly new (most had less than 100 miles) ECV trucks so I am pretty sure it is bone stock.

That would be a great engine to have. I remember seeing those when they first came available through southern metals in Wilmington 2hr away from me. I should have jumped on one of those. They were selling them for relatively little on Facebook marketplace.

when I get a chance sometime soon I’ll rig up my GoPro and drive around a bit under normal and loaded conditions. My tach, Speedo, boost and egt should all be able to get caught in the same frame. Not saying mine is set up perfect but we can compare and contrast. I’ve been interested to see how the boost and egts look on a stock turbo too.

mine is relatively smoke free except if I bog it down a bit in OD like on a hill at 40 mph. Then it just chugs along at somewhere near 1400 rpm and slowly accelerates but throws a bit of smoke. I usually manually downshift it as my 700r4 won’t downshift unless I really floor it or it slows down more.

 

[Mogman]

So it was Southern Metals, I obviously did not remember correctly, Thanks
I do have a extended billet compressor wheel in the turbo I built.

 

[Mogman]

Well the muffler delete made a significant difference, heck I pulled the Corpus Christi ship channel bridge (the closest thing we have to a mountain around here) at 68 MPH in 6TH gear! using much less throttle at any given speed and the fuel gauge does not seem to move as fast as it was before.
The fan is cycling in all conditions but still has more on time than off at highway speeds.
Guess now I just wait for the EGT and boost gauges to get here.

 

[Mogman]

OK, I may have found an issue, I noticed some moisture around the top of the coolant tank, so I got out the handy dandy coolant test kit and I'll be danged, every screw holding the brass neck to the top of the coolant tank was loose, after tightening them down it will now hold 15LB.

This would likely allow coolant to boil in some of the hotter parts of the engine because of the lack of pressure, this would send "bubbles" all through the cooling system likely causing issues, we will see tomorrow if there is any improvement.

 

[Mogman]

I did not notice much change in the ride this morning, fan running nearly normal at 75 with a tail wind, running all the time pushing a 24MPH head wind at 70MPH, but I am also running in 6th where the 6.2L would be running in 5th so the fan would be pulling more air.

BUT it looks like the joy riding is over for a while at least, I discovered what looks like gear oil coming out of the air filter box, which makes no sense because I just checked all the fluid levels about 500 miles ago (I have put over 400 miles on the GEP since I got the wheels back on Saturday)

And I just plumbed in the 6L80 into the vent system when I did the motor swap, I sure hope I did not contaminate the transmission, it takes about $150 worth of fluid and I would have to change it several times if contaminated, it would be an expensive lesson to learn.....

I will be disconnecting it and run an independent vent line as I had done when I installed the transmission. JIC

 

[Mogman]

Wellllllll, maybe it had been a little longer than I thought on the hubs, the right front hub was way over full, looks like diesel/gear oil which would make sense because I recently replaced the mechanical pump with an electric because it was leaking around the seem where the top and bottom of the pump was crimped.

It was almost as "thin" as diesel so put some on a rag and it lit up just like diesel would although it still smelled like gear oil.

So I have quite a few miles on the right front hub with contaminated gear oil

TC was right on the money and I did check it and the transmission on Sat. so hopefully that is a good omen for the transmission..

Trans still looks red but I cannot tell if it is over full until the morning as I check it at around 85 deg. and it does not have a dipstick.

A complete gear oil drain and refill is the first thing on the agenda..

It's always something!!

 

[Mogman]

A few inches before the exhaust goes into the turbo and after both sides exhaust flows have merged.

I did get the Pyro installed today and went for a test drive, the gauge sat at 900 at highway speeds, this is lower than the DuraVee would have registered, it would have been around 1000 deg.
This is all much lower than what you are seeing, but I am doing 75 not 55

 

[MattNC]

I did get the Pyro installed today and went for a test drive, the gauge sat at 900 at highway speeds, this is lower than the DuraVee would have registered, it would have been around 1000 deg.
This is all much lower than what you are seeing, but I am doing 75 not 55

Nice! I’ve not even had a chance to start mine in a week and now I’m shipping off to Boston for the week. Maybe later this week I’ll try to get some videos captured. We’re taking it and the M1102 trailer camping again once I return from the work trip.

 

[Mogman]

Nice! I’ve not even had a chance to start mine in a week and now I’m shipping off to Boston for the week. Maybe later this week I’ll try to get some videos captured. We’re taking it and the M1102 trailer camping again once I return from the work trip.

I would be interested to see how fast it reacts, your numbers are very low, when you are running at highway speeds and lift off the throttle it should drop very fast to around 300 degrees otherwise it is being influenced by the manifold (tip of probe not in the middle of the stream or cheap probe)

The DuraVee acts correctly, the Detroit only drops to around 450 degrees and then only after a minuet or so to 300 which means the turbo housing is effecting the reading, I suspect I am closer to 1000 degrees at 75MPH, the probe was shorter than I need to get into the middle of the stream so I have ordered another.

On the DuraVee you can rock the throttle back and forth and get an immediate response with very little delay, half second or so