tips on installing turbo - Diesel Forum

beleive · 12-30-2007, 01:20 AM

just got a 91 E-350 with 7.3 diesel.Has 90,000 original miles,been garaged kept this thing is nice for the age.Anyway going to use it for work,will be doing some pulling with it,want to install a turbo,know one problem is the 21:1 compression probably cant take alot of boost,so here is some questions.(by the way the trans has been redone)Would it be helpfull to do some intake work as far as porting?(Im capable of doing this)Would a big the better intercooler help alot?How much boost is to much?Would water injection keep temps down in combustion and keep from burning things up.Have found a kit,willing to do some extra work if its worth it?IF not will just buy it and install it.Thanks for any info.

91diesel · 12-30-2007, 09:56 AM

I havent seen much success with these engines and water injection. Porting might help airflow on a nonturbo and probably would help more if you had a turbo.

If i had the money...id buy a complete turbo kit right now for my truck. If you dont do any work to the internals of the head dont expect to get any higher a than 13 psi. Any more and these engines will start to fail. A turbo will definitely make you happier though. no experience on intercoolers

arthurgoboom · 12-30-2007, 12:26 PM

I've seen a few articles on the web about water injecting an IDI. It seems to work, the weak point is just the head gaskets. Apparently when the water injection comes on, boost will go from 10 to 15psi in a snap and the EGTs will stop climbing. I think that's a mod that you'd only want to do if you were looking for extreme performance though.

As far as porting, after several years of using a flowbench to develop high performance engines, I have found that a smooth surface finish to the ports will make a measurable difference in airflow, and it does matter even if you are turbocharged so don't let them tell you otherwise. Better airflow is a reduction in resistance to flow, regardless of manifold pressure.

A charge air cooler would help too, but the effect isn't as great until you get to boost pressures above 10psi where the air starts getting heated to more extreme temperatures. I'd also say that's an extreme power mod, if you wanted to go really fast, or had lots of money with nothing else to do with it

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icanfixall · 12-30-2007, 01:43 PM

These motors like any diesel just compress the air going into them. So cleaning up the ports will really help. Port matching is really important too. You can make the port finish a mirror finish if you want and it will flow better too but thats asking a lot of you. Mine are finished with a 3M Scotch Brite wheel and they do shine. These heads are really ruff in the ports so cleaning them up helps. Don't stop at the intake or the heads. Clean up the exhaust manifold logs too. Remember they have to move all the exhaust thru one small outlet especially on the drivers side manifold. It really a tight turn on the trucks but not too bad on the van manifolds. A splash water-methonel injection system will keep things cool. Most just use blue window washer fluid instead of water. It works out better. These motors with a turbo run 10 lbs of boost very easy but... Anything over 12 lbs is so heated (about 300 degrees) by the spinning turbo blades that the power gains are lost. An intercooler will thke care of the heat or water injection will do the same thing. Finally, if you try to do these modifications without head studs you will not live too long. The stock head bolts can't handle the boost pressures for too long. Get a set of studs. Right noe there are 3 places to get a set of studs for the 7.3 idi motors. The stock new head bolts I had tested to failure broke at 153,000 psi. My DPS 1/2 inch studs break at 270,000 psi and can be reused as many times as you like. Kinds like a Top Fuel motor which are 9/16 and they break at 220,000 psi.

asauer · 12-31-2007, 12:57 AM

Actually, as far as port work goes it is better to NOT have a polished finish. A little roughness will actually produce higher velocity air flow. You don't want it rough, but very light machining marks actually flow better. I'd have to find a picture to describe it, but a small amount of air 'tumbles' along the edges of the passageways and keeps the center mass moving.
The shape/cross section/volume of the runners comes into play MUCH more than how smooth the finish is.

bwood454 · 12-31-2007, 03:08 AM

so what is the weak point. the head bolts or the head gaskets? Does the extra clamping force provided by the head studs only delay the eventual gasket failure. Does anyone offer a better head gasket like the mls gaskets made by Cometic?

beleive · 12-31-2007, 03:45 AM

I use to race cars,had problem with blown headgaskets,we went to o-ring with copper gaskets,still have water leakage,then went to cometics solved problem.Answer your questions Id say headgasket.Bet cometic would custom make some.As far as polish versus machine finish on a port,we'd leave intake side with sanding roll finish,keep fuel from puddling,but the exhaust we'd polish.OF course we wasnt running a turbo,bet turbo guys polish,plus we was running carbs.With injection bet polish is better.Just my thoughts though.

bwood454 · 12-31-2007, 05:21 PM

Thats how i became familiar with Cometic gaskets. Had the same problem with copper gaskets. After switching to Cometics had no more problems. I will give them a call next week to see if they would make some for the idi motor and how much it would cost.

Fordiesel69 · 01-01-2008, 12:59 AM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: beleive</div><div class="ubbcode-body">just got a 91 E-350 with 7.3 diesel.Has 90,000 original miles,been garaged kept this thing is nice for the age.Anyway going to use it for work,will be doing some pulling with it,want to install a turbo,know one problem is the 21:1 compression probably cant take alot of boost,so here is some questions.(by the way the trans has been redone)Would it be helpfull to do some intake work as far as porting?(Im capable of doing this)Would a big the better intercooler help alot?How much boost is to much?Would water injection keep temps down in combustion and keep from burning things up.Have found a kit,willing to do some extra work if its worth it?IF not will just buy it and install it.Thanks for any info. </div></div>

I had a banks setup on my 6.9L and at 10psi it had a hard time getting over 1100 EGT. Unless of course I was going up a huge hill with a huge trailer in 4th gear WOT. These engines will run forever with 10psi. No need for an intercooler on these turbo setups, certainly won't hurt, but a waste of money. Another thing that should be done, is a very slight reduction in injection timing (1-2 degrees). Rotate the injector pump to the drivers side ever so slightly. A slight bit of propane will help as well. Do a search on this.