Waste Gated Turbo in a 1st gen?

[KEENO]

Hey Jason!



I've also seen the drive pressure math before attempting this latest modification.



If you have it... Could you post the drive pressure numbers for the 12, 14 & 16's once again?



Might make for an interesting reading...



TIA..... KEENO

 

[Lil' Dog]

Umm uhh....

I don't have the "drive" numbers as it has to be measured for the different modifications to the system (injectors, exhaust, air filter type, intercooler resistance... . ) And yes I am making excuses LOL. . I don't have the numbers. I was hoping that maybe some actual numbers could be collected by the masses.



The number I do have is from my old Heat Engines book that shows the experiment and how an increase in 1 psi in exhaust pressure reduces Hp by 1. 5%, if the intake system is unchanged in flow. The balance of boost vs. drive pressure is the key to making the most power.



I hope I didn't mislead anyone as to being the keeper of this info. #ad
Don't beat me LOL #ad




Though I am very interested in the numbers.



Sorry Guys!!!!



J-eh

 

[KEENO]

Hey Jason!



I didn't mean to "call you out" on the info...



I was refering to the drive numbers I've seen published by Ted Jannetty, JD & others on the different housing sizes. The 12's do require higher drive pressure to achieve the boost numbers. The process of squeezing the intake charge more also adds to the increased EGT effect.



They are responsive though when installed on a First Gen... It all depends on preferences and the way you drive...



KEENO

 

[Lil' Dog]

Too true Keeno!!!



Just like paint color its all what you like... If you like the kick-butt acceleration, then smaller housing is the ticket. You haul 50,000# then maybe the larger non-gated variety is for you. I am sort of a hybrid, don't haul alot but don't race either.



Its always an interesting debate...



Good luck.



J-eh

 

[Matt S]

Dang. I was looking for more boost. I guess I won't waste my time with trying to booger weld it shut. Man am I frustrated with this stuff. I think I'm now looking into the Kwik HX-40. Maybe start another injector search. I can't believe these trucks can't make over 300 hp with sane EGT's. I may go try a dyno or the track again to see the differences in the 12 vs 16.



I was working the brake issues again this weekend. Had the wife all talked into a 97 reg cab for her Honda but it turned out to be sold. She likes this truck and doesn't want to get rid of it but I want more power.





Frustrated.

 

[KEENO]

More wastegate info....

Hey Gang!



There's a great posting over in the "12 Valve Engine Forum" called "Blocking off the wastegate" Wastegate Post... click here. It clearly describes the reason for a wastegate & it's function.



All my experimenting & tinkering has proven the following to me:



A completely welded 12cm2 acts exactly like a 12 w/ the pressure line disconnected.



No increase in boost is realized due to eliminating the wastegate.



EGT is not a problem.



The 12 still operates w/i the turbo's efficiency map even with the wastegate elimininated.



Fueling is still the limitation of our trucks.



The 'flutter' that I was hearing isn't the actuator bouncing on the seat... it's actually the Banks Boost gage.



I can now change exhaust housings in under 30 minutes



Jason & others are correct in their theories



I realize that this isn't scientific but it has helped me understand the limitations of my truck.



In a few weeks I'll probably re-install my 14cm2 w/ the pressure line connected and be happy w/ 26# in 5th and slightly more smoke... I just don't know!



KEENO's Fun!

 

[Lil' Dog]

Re: More wastegate info....

Originally posted by KEENO





I can now change exhaust housings in under 30 minutes

Holy crap. . . I was agonizing over what a job that would be and was gonna source it out... Too bad you're so far away. LOL I would have to drop by for coffee...



Good findings... Good to know that with the 12 cm you aren't running the turbo outside its design speed/flow map. .



If you like the 12, keep it on. IMHO.



J-eh

 

[Stab]

16cm2

Once again proving a 16cm2 housing is the best OVERALL housing for the first gen trucks! Not as quick on the bottom as a 12, but not as restrictive. Not as boostful on the top as the 21. 5, but a lot more responsive. I haul very heavy or empty!



STILL working on the compressor side! Will have the compressor kit installed soon! (HX40 housing and wheel)

 

[JFitzgerald]

Which for me??

I am reading this thread with great interest, as I am not sure which size housing is right for me. I had looked at 14 vs. 16 and price decided that one for me. Now knowing a 12 is available for a reasonable price, I wonder if that is the one I need.



My Cummins is driven daily unloaded, but tows on many weekends, and when my new trialer is done, it will be towing about 10,000 lbs.



I believe I would love the low end response of the 12, but at what speed in 5th will power drop off? Normally, I don't run over 70 mph.



Thanks for any advice on which size.

 

[Stab]

JFitzgerald,



You have the correct housing now. Spend your money else where, like injectors or exhaust.

 

[Matt S]

The operating RPM range for the 12cm housing is 1200-2500 RPM. The 14cm is 1400-2500 RPM. The 16cm is 1600-2800 RPM. I have not noticed a power drop off, just the boost doesn't build past 28 psi. There is a lot more boost in all gears with the 12cm compared to the 16cm. Heat is up about 150*. I have yet to tow with the 12cm.

 

[JFitzgerald]

Originally posted by Stab

JFitzgerald,



You have the correct housing now. Spend your money else where, like injectors or exhaust.

Thanks for the input. I think I may have written my post in a confusing way. I still have the stock housing on my '93, an 18 from what I understand. I haven't purchased a 16 yet, but had been thinking that was the size I would buy soon. If my post made you think I have a 16, is that the one you believe is correct for me? The exhaust has got to be restrictive on mine. It looks stock and has a crunch in the curve over the rear axle. Looks like an aftermarket muffler though.



Matt - what do 2,500 & 2,800 RPM equate to in 5th gear? I can figure it out, but I wonder if you know off the top of your head.

 

[KEENO]

Hey Stab! Great to have you back!



The beauty of the 16cm2 is the easy of installation & price. No Downpipe modification... Just drop it in & go!



You probably won't notice a great difference in the 16cm2 if you're coming from the 18. 5 that was OEM on the 1993. At least we didn't when we swapped out the 18. 5 on my buddy's '93 W250 CC. The 21 to 16 really is a noticeable difference though.



Still driving the welded 12... . I'm actually starting to believe that I'm seeing a reduction in EGT by 100 degrees during Highway driving. Not sure if it's just the cooler weather or if it's because of the increased oxygen available to complete the combustion process. I might of been slightly over-fueled. The boost gage usually shows 10#-12# of pressure @ 70-75 MPH w/ 650-700 Degrees on the EGT.



There is No "one" perfect housing for all... The 16's are great compromise though!



KEENO

 

[Big Don]

I would have to say the 14 cm housing is the best housing for most trucks. From my studies, the 12 is too restirctive for higher rpm's. The 16 is too slow to spool up and too much smoke when towing on the back roads with 3. 54 gears. i do recommend a 16 for trucks with 4. 10 gears running on the interstate, but 3. 54's and a 5 speed deserve the 14 to get the best lowend/midrange and still be able to breathe while high speeding them up near 3,000 rpm's. I drive my truck daily and tow with it and use it ocassionally to blow some powerchoke away. I cannot predict the best housing for eveyone, but the above mentioned is what my thoughts on this issue are. I have had alot of folks contact me wanting to buy the 16 cause that's what eveyone has. I think the 16's sell better because of the price difference.



later

Don

 

[EOliver]

So the question I have is does someone have a non-gated 14cm housing out there? The cool thing is I can now buy a non-gated 16cm and a 12cm, but is a 14cm available also?

 

[Lil' Dog]

I've asked in a thread before, I gotta say that price is a determining factor for me also. I was or am willing to give up a little performance for some $$... But some here have regreted that choice (16) and would have ante'd up for the 14. This doesn't help the decision... LOL... .



J-eh

 

[EOliver]

Me too. I am ready to go to the 12cm non-gated if nobody has a 14cm non-gated housing. I think I am gonna skip the 16cm...

 

[Big Don]

The choice for the 12 sounds good, but keep in mind if one is going to high speed the engine at all (rpm's above 2200-2400) the 12 will not flow the air necessary and the truck will seem to run out of breathe at high speeds. Low end torque will be good, but the trade off is on the high end. If a truck had 3. 08 gears and a 5 speed, then the 12 may be the correct choice, but with 3. 54 or 4. 10's the 12 would not flow enough air to have any kick in the pants on the high end witout getting hot.

I do agree if their were a 14 cm nonwastegated housing it (do to $$$$ reasons) would be the logical choice.



I cannot say their is one correct choice to be made, the choice depends on how ones truck is setup (gearing, other engine mods, etc. ). I do feel for the majority that the 14 will make your truck perform like you expect.



thanks

Don Peters

 

[BushWakr - RIP]

I went from the 18. 5 cm to the 16 and experienced exactly what was noted above. The difference is there but not significant in my opinion. It spools quicker than the 18. 5cm, it gave me a couple lbs. more boost but not as responsive as I had hoped. In comparison my brothers 14cm w/g'd housing is a better choice. In my case the $$ were really the major factor at the time. If I did it again I would go with the 14cm wastgated or not, but go 14.



FWIW



Bob

 

[J DeMaio]

Hey Guys:



I've been doing serious studying. My truck is bone stock except for the little modifications in my signature. My boost seems to be at about 12-13 pounds. My buddy has a 1997 with a 230 horse plate, he tested my truck out last night and said he thought my gauge was wrong He thought that i should be making more boost than that stock. So, what were you guys making when stock?



Now, I don't know what to do for turbo modifications. I thought about turbo modifications and installing a 16 cm housing. My truck has 180,000 miles on it. Then I thought about Piers Super Turbo More money but I believe it would help a lot. I don't really want injectors, as they cost a lot of money and look newer anyway. So turning up the screw and possibly timing advancements to get the fuel. That should get me to 230-250 horse



What do you guys think?



Thanks



John