Isuzu 4BD2T diesel swap into Suburban

[Burning oil]

Found the issue of DieselPower, much simpler way to find HP based off of 1/4 mile E.T. and vehicle weight. From the Jan '09 issue:

CALCULATING HORSEPOWER FROM QUARTER-MILE ELAPSED TIME AND SPEED


E.T. divided by 5.825, then cube the result (multiply by itself three times, ie: 4x4x4) then divide the vehicle weight by that cubed number. That gives a very close number to the flywheel horsepower. To get RWHP, you must allow for driveline loss of about 20%, so take the number above and multiply by .8 to get RWHP. This is a very close approximation, but is subject to error due to things like traction problems, transmission slip, reaction time, turbo spooling, etc.

Here are two examples of number crunching:

Vehicle weight: 8,000lb. E.T. 15.9 sec. => 15.9 / 5.825 = 2.73 => 2.73 x 2.73 x 2.73 = 20.346 => 8,000 / 20.346 = 393 hp. 393 x .8 = 312 rwhp

V.W.: 7,200 lb. E.T. 11.55 sec. => 11.55 / 5.825 = 1.974 => 1.974 x 1.974 x 1.974 = 7.692 => 7,200 / 7.692 = 936 hp. 936 x .8 = 748 rwhp

Thanks to DieselPower for the numbers, the article can be found starting on page 144 of the Jan '09 issue.

So, let's pull some numbers out of our *ss for shits and giggles for Leroy's conversion project.

Let's assume a weight of 7,100 lbs including driver and a full tank of fuel for the Burb, and after getting his Optishift dialed in, he laid down a respectable 15.4 E.T. at the local 1/4 mile "midnight test run" location. Let's run the numbers:

15.4 / 5.825 = 2.644 => 2.644 x 2.644 x 2.644 = 18.484 (I'm rounding to the nearest 3 digits after the decimal point) => 7100 / 18.484 = 384.12 hp => 384.12 x .8 = 307.2 rwhp, a very realistic number. Using the S.W.A.G. method of hp to torque (torque is approximately twice rated flywheel hp) and you get 770 lb/ft at the flywheel and 615 on the ground.

Of course, nothing beats putting it on the rollers, but that even will vary from machine to machine as well as ambient conditions such as temp, humidity and roller traction will affect the results.

Much easier to understand. I'll try to meassure out a 1/4 mile somewhere and give it a try before the second OptiShift table is programed

 

[Husker6.5]

Much easier to understand. I'll try to meassure out a 1/4 mile somewhere and give it a try before the second OptiShift table is programed

No problem, Leroy. Numbers crunching is second nature to me, as is wrenching. Was a "pit rat" when I was a little kid back in the mid '60's for my dad's sprint car team. Would help out in the garage by doing things like at age five backing up and tripping over the drain pan full of freshly drained motor oil and sitting down in it! But, I also learned at an early age the names and uses of all the tools and helped out around the garage. Race nights, if I wasn't up in the stands during the races, I'd be in the pits before or afterwards to steer the car off or on the trailer as the crew pushed. Also got to sit on my dad's lap and steer a couple of times when they'd take the car out to the track during the week to test, of course he'd keep the speed down to a fast idle, but what a thrill for a seven year old kid!

I'm really interested in your repower project because with the cost of compressed Jurassic algae rapidly approaching $4/gal and beyond, I'm looking long range to power my Suburban off of biodiesel and other alternate fuels (sorry to all you oil industry workers) as well as regearing/repowering the Suburban so that I can cruise the Interstate at 75-80 mph and get 28-30 mpg and $1/gal - all while loaded with my three kids and luggage. I really wish there was a manufacturer that made a 3.21 ring and pinion for the 9.25" AAM IFS diff, as there is one available for the 10.5" 14 bolt rear. That would drop my rpms down to 1840ish at 75 mph - right on the fat spot of the torque curve and max mpg's for the 6.5TD, all while maintaining the stock tire size and ride height to minimize wind drag and would help maximize mpg's right now.

One can only go so far improving combustion efficiency/power/fuel economy with the 6.5. The answer is in a smaller displacement, 4 cyl, torquey diesel running at lower cruise rpms, and I feel that you're well on the way to getting that.

Now, at just less than 18 mpg driving 70-75 out to D.C. and back this fall with six of us and luggage, my passengers were amazed that we were driving 700 miles between fills (damn turnpikes and the service plazas across Indiana, Ohio and Pennsylvania - not only do they rape you on fuel price, but they're spaced so that you don't dare push the envelope to really stretch your range - unless you want to either run out between plazas or else exit in the middle of nowhere and pay the toll to try and find fuel somewhere near the exit, then get back on again). I would LOVE to push the range on the stock fuel tank to 1100+ miles safely, and a 4BT or 4BD repower and gearing change may just be the answer, and more so if I am able to run on homebrewed biodiesel-used ATF-used motor oil/hydraulic oil as a multi-fuel capable motor.

 

[Burning oil]

1100 miles is just over 25mpg with the 43 gallon tank. I would think doable from the results I have so far and have heard from others.
New injectors are in my future to just so I am starting fresh. Also I have 3:73 gear if needed I can go to 3:42 like in my 96 1ton.

 

[Burning oil]

No problem, Leroy. Numbers crunching is second nature to me, as is wrenching. Was a "pit rat" when I was a little kid back in the mid '60's for my dad's sprint car team. Would help out in the garage by doing things like at age five backing up and tripping over the drain pan full of freshly drained motor oil and sitting down in it! But, I also learned at an early age the names and uses of all the tools and helped out around the garage. Race nights, if I wasn't up in the stands during the races, I'd be in the pits before or afterwards to steer the car off or on the trailer as the crew pushed. Also got to sit on my dad's lap and steer a couple of times when they'd take the car out to the track during the week to test, of course he'd keep the speed down to a fast idle, but what a thrill for a seven year old kid!

AH! the good ole days.


Another noticable difference is how quite this engine is. It is very subtle. Only a "diesel guy" might notice something different.
If you want to remain stealth the 4BD2 is a good choice.
As opposed to the 6BT Cummins swap I did. That truck was so loud everyone turned to look.

 

[Husker6.5]

1100 miles is just over 25mpg with the 43 gallon tank. I would think doable from the results I have so far and have heard from others.
New injectors are in my future to just so I am starting fresh. Also I have 3:73 gear if needed I can go to 3:42 like in my 96 1ton.

Yeah, but I'd like to leave 2-3 gallons in the tank for a little "peace of mind" cushion when out in the middle of nowhere instead of sucking fumes, like Nevada on I-80 (no slight intended to any Nevadans for being out in the middle of nowhere) between say Windom and Elko, instead of getting a "piece of mind" from the S.O. when I run out in the middle of nowhere. Having stopped and put 42.1 gallons into the factory "42" gallon tank before, as well as 17.9 into my 18 gallon tank on my old Camry in Laramie, WY, I really don't like cutting it that close on road trips. Thus I'd love to get 28-32 mpg consistently, and would prefer the other side of 30. I'm 3.73 geared too, going 3.42 like in my '94 C2500 C&C is an option, but installing a pair of 3.21's front (if available) and rear is still WAY cheaper than a Gear Vendor overdrive to get into the right rpm range for 75-80 Interstate cruising. I bought the K2500 Suburban as the ultimate family truckster for all-weather travel. It won't be hauling a 13K lb lowboy or anything like that, maybe at most a six person pop-top camper, so I'm not really worried about pulling. Just high speed high fuel mileage cruising. That's where those low rpm torque monster 4 bangers like the 4bd and 4bt shine, especially if the boost and fueling are right for maximum efficiency which leads to max power and fuel economy at a specific rpm band.

Who knows, perhaps with a frame-mounted aux fuel tank along side the frame rail, nearly coast to coast on one fueling would be possible. Can anybody say GM Suburban diesel Gumball Rally winner?!?

 

[Husker6.5]

AH! the good ole days.

Here's how good ole: Speedway Motors' World Headquarters and distribution center is 5 minutes from my house. My dad's sprint car team used to race against "Speedy" Bill Smith's team all the time, and was the only team that could consistently beat Bill's car back when we were racing. Bill and my dad have been friends for nearly 50 years! I remember when Jan Oppermann was driving for Bill in open wheel and in this was before he got his Indy Car ride and raced at the Indy 500. The vintage racing museum at the distribution center is fantastic, and the five minute drive over to Will Call to get parts sure does beat waiting on shipping and shipping costs, although there is the 7.5% sales tax issue...

REAL Sprint Cars DON'T have wings!!

 

[Burning oil]

This is awesome info Leroy. Any hwy mpg numbers yet?

Got another 260 miles on it. Mostly hwy. I was shocked to find the MPGs did not go up they stayed the same?
This was mostly 70-75 MPH. Im inprocess of getting new injectors and I want a hotter Tstat. It has a 180* now, but I want a 195*

 

[Husker6.5]

Got another 260 miles on it. Mostly hwy. I was shocked to find the MPGs did not go up they stayed the same?
This was mostly 70-75 MPH. Im inprocess of getting new injectors and I want a hotter Tstat. It has a 180* now, but I want a 195*

That should help, possible that the IP is wearing out? Also what kind of RPM are you running at that speed? That also affects MPG quite a bit.

 

[Burning oil]

That should help, possible that the IP is wearing out? Also what kind of RPM are you running at that speed? That also affects MPG quite a bit.

75mph=2000rpm
70mph=1800rpm

 

[HMF]

75mph=2000rpm
70mph=1800rpm

Your tach may be off, cause mine spins about 2000rpm at 70 with the 3.42 gear.

Not surprising with the different alternator setup. The crank and alternator pulley diameter ratio is probably not the same as the 6.5 was and that is what the tach is calibrated to.

 

[Burning oil]

I think it is reading low. My RPM cant be lower than yours as I have 3:73.
Someone mentioned a tach made by (I think) Tiny Tach? I need to get something to get an actual RPM from the crank.

 

[Burning oil]

Husker, I did two very crude runs today. I just let Appox 1/4 mile tick off on the odometer and it took 20 seconds each time.
Im toped off with fuel 43 gallons and whats a Burb weigh? 6800#s?? empty?

Even though you spelled it out for me, I played with the ET and if I give a higher ET the HP go's up. I must be doing it wrong.
What do you get?

 

[Burning oil]

OH wait I think I got it 139 HP right?

Edit: Oh crap did it again and got 176HP

 

[handcannon]

I think it is reading low. My RPM cant be lower than yours as I have 3:73.
Someone mentioned a tach made by (I think) Tiny Tach? I need to get something to get an actual RPM from the crank.

Go to tinytach)dot)com and look at their diesel tach. It's about $100, reads injection pulses from a sensor fastened to an injection line. It also has an hour meter built into it to help keep track of different things (maintenance, oil changes, etc) according to engine running hours.

I have one and it is more accurate than the stock setup. It has a digital readout.

Don

 

[Burning oil]

I have heard good things about them.

 

[Husker6.5]

Husker, I did two very crude runs today. I just let Appox 1/4 mile tick off on the odometer and it took 20 seconds each time.
Im toped off with fuel 43 gallons and whats a Burb weigh? 6800#s?? empty?

Even though you spelled it out for me, I played with the ET and if I give a higher ET the HP go's up. I must be doing it wrong.
What do you get?

I just used the calculator on my cell phone and got 134.5 RWHP based off your numbers, about 167 at the crank. The impulse signal from your tach is off, either due to a smaller crank pulley on the 4BD than on the 6.5, or the pulley on the alt you're using is larger than the stock 6.5 GM alt's. RPM @ 75 mph with 3.73 gears and 245/75/16 tires is 2250 +/-. @ 65mph 1950 RPM +/-.

 

[Burning oil]

Go to tinytach)dot)com and look at their diesel tach. It's about $100, reads injection pulses from a sensor fastened to an injection line. It also has an hour meter built into it to help keep track of different things (maintenance, oil changes, etc) according to engine running hours.

I have one and it is more accurate than the stock setup. It has a digital readout.

Don

Guess what I just bought? Also got an account set up with Tiny Tach. Ill be adding it to my product line.

I just used the calculator on my cell phone and got 134.5 RWHP based off your numbers, about 167 at the crank. The impulse signal from your tach is off, either due to a smaller crank pulley on the 4BD than on the 6.5, or the pulley on the alt you're using is larger than the stock 6.5 GM alt's. RPM @ 75 mph with 3.73 gears and 245/75/16 tires is 2250 +/-. @ 65mph 1950 RPM +/-.

Thanks Husker, the factory tach is reading low for sure.

 

[handcannon]

Guess what I just bought? Also got an account set up with Tiny Tach. Ill be adding it to my product line.

You won't be disappointed. I really like mine. I almost never look at the stock tach anymore.

Another good addition to an already good product line.

Don

 

[Burning oil]

Got 5 of the Tiny Tachs in. Installed one yesterday and the factory tach is about 150 rpm low.

I'll get some pictures later. Took about 15-20 minutes to install.

 

[deejaaa]

the factory tach is about 150 rpm low.......

is that across the entire power band?