The cummins style H (holset) turbos push more volume with less drive pressure resulting in a cooler running engine that can handle more power with less problems. You can change exhaust turbine housings on them and tune the turbo to your preference.
Read up on the different swapped turbo's the GM 8 has a small exhaust turbine and is very inefficient above 2600 rpm-ish
The latest and greatest is variable pitch turbo, its giving amazing performance and economy best of all worlds.
1999 chev suburban C2500
300,000 mi
I got the Isspro gages from Kennedy. VERY easy to read at a glance, mounted overhead. The Banks gages look about as nice, but I've only seen them in other's trucks on a pillar mount.
I also like the ISSPro gauges, I have had them on my 1995 for a long time (18 years)
2016 GMC SLT 2500 CC 4x4 Duramax All Terrain 59K
1995 GMC 2500 EC 4x4 6.5TD,236K,Custom Tuning,HX40W-II turbo,Amsoil Bypass Filter,KD Exhaust,FSD Cooler,KD Headlight booster,Hi-cap Cooling
TDP member #14
So with the motor installed. I see coolant temps get to 210-215 and oil gets up to 235. I installed a remote oil cooler and bypassed the radiator and see oil at 220.now.
I am also swapping a built 700r4 behind this 6.5 optimizer.
I installed a trans cooler in front of the radiator and temps dropped from 235 to 190 max. That’s good.
So far with a junkyard GM1 turbo with turbo master, I run about 600-700 degrees egts average. Highest at 800 degrees on 6% grade.
The max I got the turbo boost at is 12 psi by accident. Usually runs 6-9 psi.
Pictures of the Diamond Eye Exhaust Crossover, 3” Modified downpipe to 4” with no muffler or cat. Heat wrapped areas around motor. Yes! Downpipe is between frame which has to be notched a little.
Relocated coolant reserve to passenger top rear fender.
Relocated new battery trays with new batteries.
Installed 7 blade fan from junkyard. Clockwise rotation.
I like the tires/wheels! I passed up a set of H1 tires/wheels at a Washington state salvage yard some years ago. Always wished I'd bought them.
How did you solve the frame interference problem with the turbo exhaust exit? I have pictures of showing how others did it, either by constructing a downpipe that runs outside or inside the frame rail. Some creative pipe building was necessary. I think a Holset HX35 might make for an easier downpipe transition.
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After researching for hours and hours… I came across this thread and copied post #8 solution with doing the downpipe. It was the cleanest install I’ve seen yet so I went for it and it worked very well. Here’s link. Post #8
https://www.dieselplace.com/threads/...wnpipe.830386/
Here’s Pic of the remote oil cooler under the blazer in the rear. It reduced my oil temp by 15 degrees. Pulling a long 6% grade, my oil temp went from 235 degrees to 220 degrees. I might add a dual oil cooler to reduce the oil temp even more.
And here she stands tall with the beadlocks and tires on! It does vibrate some at the current top speed of 55mph. I will add more dynabeads and get an alignment done.
Yeah back then you would have scored big if you got that set of beadlocks. Nice to air down to 0-10 psi for that added traction and softer ride on the trails.
I do have another new soft top but I am trying to get another year or 2 out of this old one. Had a tree fall on this one a few years back on the trails.
Still think an HX35 would make for a cleaner install and better performer - then, the downpipe would look a lot like that use with the Banks Sidewinder 6.2L turbo system when using the factory 6.5 manifold. I like that you were able to use the factory 6.5 exhaust manifold (not having factory A/C in your Blazer made it easier). The Banks exhaust manifolds are exceedingly hard to get these days. Jim
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I called Banks early this year and they said they have less then a dozen Sidewinder Exhaust Manifolds left. I had 2 1/2 banks sidewinder kits on hand and 2x Hx35w’s. I decided not to do the banks or the hx35w and sold it all. To me, in my mind, it did not make sense to put a banks kit on because of hard to get parts availability. As for the HX35w i did not want that either because dyna testing showed that one would have to darn near redline to get decent boost levels. Right now I am extremely happy with the low rpm spooling of the GM1 turbo I have. I can easily get to 15 psi but choose to keep boost levels around 6-9 psi with the turbo master.
Bostic motors recently came out with a turbo kit for 6.5 motors.
According to the compressor flow maps, the GM series of turbochargers are limited in efficiency to about 2200-rpm with a pressure ratio of 2 (15-psi). Above that RPM, the boosted air temp requires an intercooler and the small turbine produces an increasing amount of exhaust backpressure (high EGTs).
Dyno testing the 6.5/HX35 & boost levels.... I'd love to see the actual data... What you're reporting isn't what we found.
https://www.thedieselpage.com/member...rysholsetc.htm
https://www.thedieselpage.com/member...ylernelson.htm
The GM series of turbos do a great job for what they were designed for... light-duty, low smoke, quick spool. In an off-road environment like what your Blazer looks to be built for, the GM turbo may be the best choice. Heavy towing and high power demand is where the GM turbos fall down. The single regret I had about our 6.5TD Power Project was not installing an HX40. That turbocharger would have allowed that particular engine to reach its full potential. Jim
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It won’t let me see it. At what boost levels were your tests at when reaching maximum performance with the hx35w?
My buddy had the 6.5 with banks manifold and an hx35w and claimed that it was sluggish until 3000rpm and 20+ boost which pulled the head studs out of his block. His advice made me weary.
Charge air pressure is just a number. There are a LOT of numbers. If you choose to account for only one, such as boost pressure, you'll have less performance and a lot more wear/tear. The GM turbos, as Jim said, have a specific job to do, and they do it well. Outside of that, and they are baggage. Higher intake air pressure is useless if the other side (exhaust back-pressure, for example) counters it. The engine is doing a lot of work, but it doesn't get to the flywheel. A lot of research has gone into turbo efficiency. Use it for what it is.
You must be a paid subscriber to access TDP articles. If you are serious about GM Diesel powertrains, it's the best investment you can make. Everything you're trying to do has been done, and that's where it is.
TDP is where people come for solid, proven and reliable information... anything 6.2/6.5 related.
Here's an article that's available to everyone. It adds to the discussion about the 6.5 and 20+ lbs of boost pressure. No studs were pulled... Skip down to the part about Ron Schoolcraft's 1995 6.5TD K2500 Suburban. If I remember correctly he was using a modified HX40 or something similar.
TheDieselPage.com's July 2006 Pull-Off
Peninsular Diesel produced performance marine 6.5 diesels for years.... all running with big turbos, big boost and 18:1 pistons. TDP published articles about them, and I/we visited their operation in Michigan. They always used the TTY factory head bolts. Not a single mention of pulled head bolts in all the years I talked to them...
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Yes to my knowledge 18:1 pistons will drastically change the amount of boost levels and make it safe to run. Everyone I have talked to that has done an hx35w with stock pistons eventually killed their motor while daily driving it. Too costly to change pistons. I already got $10,000+ just into the motor so far.
"Everyone"? "Killed their motor with an HX35 while daily driving"? "Pulled the studs"? My BS detector is flashing...
Combustion pressure can be up to 3500-psi at full power. If the exhaust is clean, how can going from the stock 7-psi boost pressure produced by a GM turbo to an efficient 15-psi from an HX35 or even an efficient 20 from an HX40 hurt a 21.3 CR engine? By the way, I only advocate for 7-10-psi from the GM series of turbos, 15-psi from the HX35 - 20-psi from the HX40, all because of efficiency - cool boost and low backpressure. In gradation, anything over 7-psi boost pressure requires an intercooler and a performance exhaust system.
I'm putting a 1994 6.5TD Blazer back together right now that was a victim of too heavy a right foot while towing and an inefficient turbocharger for how this Blazer was being used - i.e. high EGTs due to a turbocharger with a too restrictive turbine/compressor (GM-4). The prior owner was also running a Turbomaster and a performance chip, and wasn't paying attention to the EGT/Boost gauges as the pistons melted around him.
Also, by the way... 18:1 pistons are only recommended for those who tow a lot or are running a boat. Not for daily drivers. 18:1 pistons allow people to add fuel and boost to make more power (build more combustion pressure), while giving the engine more heat rejection capability. The Diesel Page has discussed all this to exhaustion in years past. In the tens of thousands of 6.5 owners I've communicated with over the past 25 years, I've only heard of maybe 1 -2 examples of pulled threads in the block deck, and this was due to a rotten block or damaged threads, and it happened during a head installation - not from turbocharging.
Final by the way... Some years ago I attended a local diesel dyno event where Heath's 6.5 shop truck was there to spin the rollers. That 6.5TD powered 1995 truck was running (or so they said) 21.3 Cr pistons, a Turbomaster on a GM turbo, his custom programming, propane injection, nitrous injection, water/meth injection and the kitchen sink.... I've heard thousands of diesel pickups run at dyno events - from lots of stock trucks to 1000-horsepower super trucks. That 6.5 sounded way-way different - raspy and scary - I stepped way back..., but it made 300 rear wheel horsepower for the 1-2 seconds it had to. Then, they drove it back to Washington state after the event, or at least that's what they said they were going to do as they left the event. I reported all this right here in The Diesel Page at the time. That engine didn't pull the head studs or bolts, or whatever the engine was equipped with. That was certainly no daily driver, and I sure wouldn't want to tow a 10K trailer out of the Columbia river gorge on I-90 with it - with all that stuff switched on.
Last edited by More Power; 11-15-2021 at 17:52.
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