M998 turbo conversion

[MattNC]

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

Alright, as promised I finally got some videos of it running. They are a bit long, but I just left the gopro running and figured its more data. I'll post some pics of the EGT probe location as well.

My ongoing restomod M998ish project

I thought I’d share my restomod project that’s ongoing and progress so far. I use the truck a lot from the beach, to the farm, camping, Home Depot runs, etc so I made the truck to do what I want it to do while hopefully honoring the 30 year old military vehicle it is. Base vehicles- 1993 M998...

www.steelsoldiers.com

 

[Mogman]

I put a boost gauge on it and am rather disappointed with what I am seeing, but also a little confused at what I am seeing.

I am running around 7psi at 75mph and 2200 rpm, if I lift my foot and then get back into it it will jump to 10psi for just a second then drops back to 7 psi.

Another thing while accelerating the boost drops off as the rpm increases

I guess I will try to build an adjustable waste gate controller as I have not seen an aftermarket manual controller for the GM-7 center mount.

That should not be too hard to build...

 

[MattNC]

I put a boost gauge on it and am rather disappointed with what I am seeing, but also a little confused at what I am seeing.

I am running around 7psi at 75mph and 2200 rpm, if I lift my foot and then get back into it it will jump to 10psi for just a second then drops back to 7 psi.

Another thing while accelerating the boost drops off as the rpm increases

I guess I will try to build an adjustable waste gate controller as I have not seen an aftermarket manual controller for the GM-7 center mount.

That should not be too hard to build...

Your numbers sound like what Logan Turner posted on the HMMWV owner’s Facebook group for a baseline run with a stock turbo truck. He then added a wicked wheel, turned the pump up 1/3 turn and added a manual waste gate and has a video on the freeway at 80 mph with 17lbs of boost!

 

[MattNC]

Your numbers sound like what Logan Turner posted on the HMMWV owner’s Facebook group for a baseline run with a stock turbo truck. He then added a wicked wheel, turned the pump up 1/3 turn and added a manual waste gate and has a video on the freeway at 80 mph with 17lbs of boost!

to you other question he said he bought the manual wastegate kit from BD Diesel.

 

[Mogman]

to you other question he said he bought the manual wastegate kit from BD Diesel.

Do you have a link???

 

[Mogman]

Found it!
Boy that really did bring down the EGTs also!!

 

[Mogman]

I bought one from Quick Tricks, KDB does not have one.

 

[Mogman]

Alright, as promised I finally got some videos of it running. They are a bit long, but I just left the gopro running and figured its more data. I'll post some pics of the EGT probe location as well.

My ongoing restomod M998ish project

I thought I’d share my restomod project that’s ongoing and progress so far. I use the truck a lot from the beach, to the farm, camping, Home Depot runs, etc so I made the truck to do what I want it to do while hopefully honoring the 30 year old military vehicle it is. Base vehicles- 1993 M998...

www.steelsoldiers.com

I guess I should have just kept the 6.2L and put on a BMI kit, not sure what the kit cost, I only paid $1500 for the 2007 GEP turbo with 100 miles on it, I did have to build a turbo for it.
Is your M998 a A0 or A1 with the 2.56 gears? I am seeing 2200@75 with the 6L80, it has a somewhat lower ratio 6th than the 700R4, the 700 is I think .75:1, the 6L80 is .67:1.
I am running stock size tires
EDIT, also have you weighed your truck, my helmet top (Detroit) weighs 7400lb, I would guess your truck weighs around 6-6500, and that dang helmet top is a Real drag, like an open parachute.. I think an ambulance would be even more aerodynamic.

 

[MattNC]

I guess I should have just kept the 6.2L and put on a BMI kit, not sure what the kit cost, I only paid $1500 for the 2007 GEP turbo with 100 miles on it, I did have to build a turbo for it.
Is your M998 a A0 or A1 with the 2.56 gears? I am seeing 2200@75 with the 6L80, it has a somewhat lower ratio 6th than the 700R4, the 700 is I think .75:1, the 6L80 is .67:1.
I am running stock size tires
EDIT, also have you weighed your truck, my helmet top (Detroit) weighs 7400lb, I would guess your truck weighs around 6-6500, and that dang helmet top is a Real drag, like an open parachute.. I think an ambulance would be even more aerodynamic.

Glad you found everything. I think your truck is awesome and from that other post with the manual wastegate I think you’re really close to it being perfect. These engines seem to need some air to wake up.

The kit was around $4200 and has everything but I do need to reroute the exhaust this summer as it leaves the exhaust as the low point which I personally want to change. So not cheap or perfect but doable for me.

my truck is a plain vanilla A0 M998. Some upgrades has been done such as 10k half shafts but otherwise it’s 1993 stock, well before the turbo and 700r4. The diffs are 2.56.

when I first got it and weighed it the truck was barely over 5000 lbs. it’s gained some weight with a few minor additions but also lost some with wheel and tire changes. It does benefit from being light.

 

[Mogman]

I canceled the boost controller, I talked to KBD and they said they did not have them cuz it was just too easy to mod a stock one..

 

[REF]

I purchased both the Wicked Wheel 2 and turbo boost controller at the same time from the same place, For what it's worth my 2004 M1123 with a take out GEP turbo engine sits at a solid 10 PSI boost while accelerating and sits there while cruising 55 to 70 with the spring adjusted to 2" . At this point I don't feel like i need more boost until I add more fuel.
https://www.dieselsite.com/turbomaster1996-2000cktrucks-2.aspx

 

[Mogman]

Well that was REALLY easy, just grind off the crimp in the middle of the "can" until it gives up the "cover", then carefully grind the end of the rod (spring end) until the spring cap is free.
Then thread the rod with a 10-24 die and drill the spring cap to slide over the rod and presto manually adjustable boost control.

Unfortunately the E clip where the boost control attaches to the waste gate snapped so I have to dig something up before test driving it, I do have it "wound up" a little tight..
I will likely back that off a little before testing
EDIT, found a clip so I will see what there is to see in the morning.

 

[Mogman]

I purchased both the Wicked Wheel 2 and turbo boost controller at the same time from the same place, For what it's worth my 2004 M1123 with a take out GEP turbo engine sits at a solid 10 PSI boost while accelerating and sits there while cruising 55 to 70 with the spring adjusted to 2" . At this point I don't feel like i need more boost until I add more fuel.
https://www.dieselsite.com/turbomaster1996-2000cktrucks-2.aspx

The pictures of the Wicked Wheel and the billet wheel I got from KBD look exactly the same, I suspect there is one manufacturer of the billet wheels and everyone puts their brand on it.
So I should get similar results..
EDIT, I think you are right on, on the 10 PSI, I will be happy with 10-12 PSI

 

[Mogman]

OH HELL YEAH!!!
BIG difference, boost went to a solid 10 PSI with the above setting, EGTs came down about 75 degrees and it takes less throttle at speed,
It has to be getting better fuel mileage and the GEP seems much happier all around.
I may try for 12 PSI but I see no reason to turn the pump up at this time as it has enough power to run around the Coastal Plains

 

[MattNC]

Awesome, that has got to feel great. I am really pleased with where I am at with mine and I am not trying to drag race just make it a much more usable truck, which the overdrive and 10psi boost does very well. I don't want to start seeing what else can break if I push it to hard. BMI had me turn the injector pump up 3/8 of a turn from the stock NA and it seems to be just right, maybe just a bit rich at low rpms. If I let the engine chug along up a hill at low rpm, lets say 1200 rpm, which it will do without losing speed, I do throw a bit of smoke until I force a downshift and the rpms and boost come back up. I wonder if the wicked wheel would help at low rpms get a bit more boost and help burn cleaner? The boost at low rpms like 1200 and chugging along is around just 2-3 lbs.

 

[REF]

Mogman;
You might check your injection pump P/N, the DB2831-5485 pumps were on late model HMMWV engines and that's as good as it gets. DB2 - 8 cyl-3.10 plungers and 5485 were set for 200HP from the factory. also I set the spring length on mine to 1 3/4" on the boost controller and under hard acceleration I am pulling 12 LBS boost, and cruising at 55 - 70 runs constant 10 LBS.

 

[Mogman]

Mogman;
You might check your injection pump P/N, the DB2831-5485 pumps were on late model HMMWV engines and that's as good as it gets. DB2 - 8 cyl-3.10 plungers and 5485 were set for 200HP from the factory. also I set the spring length on mine to 1 3/4" on the boost controller and under hard acceleration I am pulling 12 LBS boost, and cruising at 55 - 70 runs constant 10 LBS.

I cranked mine up a little more, running 11-12 psi max and around 10psi cruising, will have to check on the pump, I am getting my butt handed to me right now by my JD 350 dozer....

 

[Mogman]

Problem: fan runs all the time on the highway.
Theory: the thermostat is controlling the temp high enough to keep the fan running all the time.

So I ordered a 180 deg thermostat and yesterday is was on the truck for delivery so I drained some coolant, removed the original thermostat and had everything ready only to find I ordered the wrong thermostat so I just put it together without the thermostat and would try just letting the fan control the temperature.

Got her up to highway speeds and it went to 200 deg and the fan came on and stayed on and the temp stayed at around 200 deg.

One thing I noticed is the cooling system has one glaring flaw, on all high performance diesel engines (Cummins, Duramax, ford) they shut off the bypass when the thermostat opens routing ALL the water through the radiator, NOT SO with the Detroit, it has a huge hose that bypasses the radiator and it still does when the thermostat opens, NOW I understand why the Detroit water pump moves nearly three times the water as the Duramax water pump, it HAS to to TRY to overcome the fact the bypass is open all the time, geez what were they thinking???

So the "new" theory is that the aluminum radiator has more back pressure due to the smaller tubes which exasperates the problem by encouraging more water to flow through the bypass and less through the radiator...

So the next step is to have the OEM radiator cleaned and checked and rebuild the stack again, I will also talk to the guys at the radiator shop about the possibility of fitting a "super core" to my tanks.

 

[MattNC]

Thanks for sharing the differences between the stock and aftermarket radiator. I was thinking of one of those but this makes me rethink that. My turbo is certainly different but I've not had temp issues at all even on hot days with a heavy load. The fan cycles on every few miles and on hills but not constant. The overdrive helped dramatically as well by not running 2800+ RPM all the time on the highway.

 

[Mogman]

The aluminum radiator does great with the Duramax, of course it closes the bypass so all the water must pass through the radiator.
I may look at restricting the bypass on the GEP to see if that helps