time for new turbo...

[jaynes]

So my truck is an early '91, so I'm assuming that it has the 18. 5 cm2 housing on it. Would it do me any good to switch to a 16cm? Or would I have to go to a 14 to notice any difference?



jaynes

 

[dpuckett]

I would suggest with your 3 speed auto, staying with the 16. Wont add MUCH, but it should lower EGTs a bit. I put a 12 on mine, with 4. 10s and 5 spd, and if I towed a lot, I'd put on a 16. A 14 may work well, too, depending on your driving habits and what you do, but I have no experience with them, so cant say for sure. I think a 12 is a little much for towing with low gears or no OD. Just my opinion, though.



Daniel

 

[jaynes]

Well I don't do any towing, it's just my fun truck. And I drive around in town quite a bit, and there are some hills that require me to give er alittle more pedal than normal. So all in all, I stop and go quite a bit and go up some pretty steep hills regularly. I do do abit of highway driving at WOT. It only goes 80 mph, so thats why I run WOT. Any more thoughts on turbo sizes for me... besides my 18. 5cm2? Thanks!



jaynes

 

[jaynes]

..... anyone?

 

[cerberusiam]

Do you want stop light to stop light performance or better highway running? Since you run at WOT a lot of the time a smaller hot side could impact that. I would keep the 18. 5, change the compressor to a HX35, and add some injectors for more fuel. That should boost the bottom end a bit and preserve the mid and top end for EGT control and towing. Just a thought.

 

[Smokin 90]

I just put a HX35 with a ported 18. 5 on my truck and I am very happy with it . I mostly drive on the highway and the truck will pull hard to 65 and then start to ease up a bit but I can still hit 85 - 90 if I keep my foot in it.



With the HX 35 I see about 32-33 PSI boost and egt's around 1225- 1250 with a 70 mph cruise egt of 800 degrees. My pump is turned about 2 turns past the lock collar and my fuel cone is turned to the steep side of its profile. With this combo I have gotten 206 hp and 526 lbs/ft of torque and I know that there is more if I do some tuning.



Hope this helps,

Kurt (smokin 90)

 

[JLEONARD]

I changed from a 18. 5 to a 16 on my truck. It gave a mrked improvement in drivability.

Most of my driving is highway, and the 16 makes a huge difference in power on the entrance ramps. In the 50 to 80 mph range there is no turbo lag and the power to pass is there instantly.

My truck will still easily hit 90 + (been to 100) but I have to "push" the truck a little more than I did with the 18. 5 housing.

Oh yes, I did port the 16 when I installed it. Don't know if that helped much, but it's so easy to do that I felt I had to.

I can get 27/28 psi of boost at 70/75. All I've done to the pump is turn the fuel cone and starwheel.

Hope this helps.

 

[BushWakr - RIP]

Generally the difference between the 18. 5cm and the 16cm is some faster spoolup, about 2-3psi more boost and some smoke improvement.

As noted in the last TDR mag the 16 and 18. 5 don't have any marked difference in terms of top end performance and the EGT differences are very hard to find except at the most extreme end of the "tweak range"... .



You can make some improvements to your overall top end speed by increasing your high idle or governor setting. These engines seem pretty happy when run up to 3000 RPM as a daily driver.

On the highway you should have no problem with that. You'll have the speed (airflow) minimal loading, and enough RPM to keep things cool... . again assuming you haven't gone to the extreme in fueling.

Porting a basic 16 or 18. 5cm housing will help reduce some of the potential drive pressure issues at the upper end. (back pressure at the inlet to the turbo exhaust housing).

This will help to extend the upper end a bit. Too much porting or opening up can result in reduced velocity entering the turbo horn and can make a bit of lag possible... and you're trying to reduce that right... . . .

Just port a bit, without going too far. The gasket pattern is a good guide but don't go right up to the gasket edge. Just smooth the entry to the exhaust inlet, and go in about 1 1/2" or so, smoothing as you go.

Also keep in mind that the walls of the exhaust housing inlet are not overly thick so watch how much you take out.

Since your doing this to the exhaust housing why not take the exhaust manifold off, and do it too. Again, go easy on the amount of "wall thickness" you remove. It too is not overly thick. Like the turbo inlet, taper the inlets to the manifold, smoothing as you go.

Just reach in as far as you can and take the roughness out.

Last, there are two bolt holes on the exhaust manifold that are smaller than all the rest... I don't know what they were thinking, unless it is to "locate" the manifold. Anyway, find a drill bit just one size bigger than the two small holes and open them up.

This will help reduce the gasket creeping, and reduce (not eliminate) the possibility of breaking an "ear" off on the manifold under high heat/load.



Pastor Bob.



Remember this is a pressurized system so glass smooth is not needed. Same thing on the intake manifold side... you don't need a mirror surface since boost air is being pushed in, not drawn or sucked in like a gasser.

The next step would be to save a couple bucks and go with a hybrid turbo like the HX35/16.

 

[MSilva]

1992 Turbo

What is the easiest way to check if the turbo is working? My 1992 turbo does not whistle like in my 2003 truck.

 

[Joseph Donnelly]

Jaynes, your housing may be a 21 cm2. Look on the back side of the housing near the mounting flange going to the manifold. The size is cast in. The 21 is very sluggish and won't work well even with 400 hp to spool it.

 

[jaynes]

So would a HX35 with a 16cm housing be the best bet? I mean it seems really sluggish, and 90% of my driving is stop and go. But when I drive on the highway, it's WOT all the way. I also have a 3 speed auto and I don't pull anything. I use it strickly for driving, no hauling. Would the HX35/16cm combo be my best bet?



Jaynes

 

[JLEONARD]

FWIW, that's would be my choice.

Jay