Can an aftermarket turbocharger kit be made reliable at low boost levels?
There is a turbo kit for the Hummer H3 with the 3.7 engine. They make all kinds of wild claims about 450hp which I'm sure will kill the engine in short order if it's not built for it.
Suppose you only dump 4-8 pounds of boost into a stock engine and bump the HP from 250 to 300-325. Can that be made reliable with a conservative tune?
I wouldn't be surprised if that 8 lbs of boost with a properly sized turbo gets you in the 400hp range with a fairly modern 3.7l engine.
I would think you can definitely make 350 reliable hp out of 3.7l
Opposite end of the spectrum, but I am making almost 240 rwhp on a stock Miata 1.8 bottom end with a supercharger pullied for 10 psi at maximum boost. The car is dead nuts reliable and has been for 15 years.
It's all in the details of fuel delivery and ignition timing.
One thing to keep in mind whenever anyone says "my stock block has been making 2x hp for 100,000 miles!" or similar transmission claims is that they may or may not be actually producing that power on a regular basis. Just because it might make some power at full boost does not mean they ever actually do it. You can slap on a turbo capable of 8psi and never actually build more than vacuum. If you are regularly making full hp, well, it will have a shorter life for sure. That's just how things work. Will the life be longer than your ownership will be? That's the real question with no answer.
I don't have any expert advice to offer, but I'd love to see the build thread if you go through with it.
A turbo H3 sounds like a lot fun.
If it's the 3.7 you're concerned about, those atlas motors are very well built. As long as it's in good shape to begin with and the tune is done right I would have zero concerns. It should be very well documented online
Make sure your cooling system and intercooler are up to the task, be conservative with ignition timing, make sure the turbo isn't going to surge or be way outside its efficiency range, make sure your oil temperatures stay under control and the turbo oil drain actually drains, and you should be fine at low boost. I've done it and only had issues when cranking up the boost and getting greedy with ignition timing on an engine with no knock control.
Enough cooling + good tune = should be fine...............as long as you aren't constantly abusing it. A quality tune from someone who knows what they are doing is incredibly important.
I've been considering the Harrop Supercharger for the BRZ as on the stock fuel system it still gets you up to ~300whp (up from around 205-210whp). And since I won't be tracking the car or abusing it, I'm pretty confident it would be just fine.
There's a GRM forum member who has turbocharged his Buick variant that uses the Atlas and it seems to be handling the increased power just fine. He's got YouTube videos and a thread.
Thousands of our Miata customers say yes, it is possible. The biggest danger is how easy it is to just add a little more boost. Be an adult, stick to the designed boost level and enjoy.
I've had my 'cheap and entry level' GReddy turbo on my Miata now for 24 years. Still works, never rebuilt and makes me smile.
I built a turbo engine for my 88 Fiero and drove it for over a decade with zero issues. I always figured that 10 psi maximum boost was a good place to stop without an intercooler. Gave around 300 bhp on a stroked 3.2 engine.
Doing the same thing with my Solstice coupe which does use an intercooler and runs up to 25 psi once in awhile for c. 375 bhp out of 2.0 engine and also zero issues in the last 15 years.
I'd say that it depends entirely on engine design and strength - you can trash a less than sturdy engine very quickly if you use too much boost, but 10 psi or less should be pretty safe with most engines.
The only problem with the Miata is that it was a turbo engine that Mazda decided to sell naturally aspirated, so it had a lot of headroom in stock form.
The Atlas seems to be one of those Schrödinger's Engines that is simultaneously tough and overbuilt, yet some claim that they blow head gaskets constantly and the head bolts are so fragile that they may break in service. Or when installing new ones.
Its not hard to throw a couple lbs of boost and keep it reliable. I did it to an old subaru rs 2.5 long ago. The big deal is just correct tuning.
I'd be more worried about the reliability (and, by association, quality) of the aftermarket turbo kit itself than of the engine under boost.
I will skip the soapbox tirade, but in a world where we mostly buy online, where we can't examine things in person or beat the seller's door down if he sells you junk, it can be tough to know you're getting quality.
In reply to cyow5 :
Absolutely. I have a boost gauge with a pilot light when it goes above zero. That light only comes on near WOT.
DarkMonohue said:I'd be more worried about the reliability (and, by association, quality) of the aftermarket turbo kit itself than of the engine under boost.
I will skip the soapbox tirade, but in a world where we mostly buy online, where we can't examine things in person or beat the seller's door down if he sells you junk, it can be tough to know you're getting quality.
My OPINION is that if you understand what is critical and make that part / system correct, you are fine with cheap turbo kits.
Make sure your fuel pump is good. Make sure your timing is good. Make sure your injectors are up to it. Make sure your wastegate is correct. Make sure your turbo oiling is correct.
It should hold up, even with cheap parts. It just won't be as good as it could be!
In reply to wvumtnbkr :
That's fair enough. My greater concern is with metallurgy and craftsmanship of things like the turbocharger itself. Most real garbage can probably be identified by careful inspection before it is pressed into service.
The turbo BRZ was so much fun the only thing that got me to sell it was finally finding a GR Corolla. It did have decent cooling vents in the hood & wasn't very aggressive.
So, I'm going to move forward with this project. The kit showed up yesterday.
In reply to DarkMonohue :
The kit was all of $1300 so the quality is probably suspect.
That said, the manifold looks to be fairly well-built and stainless. Nice thick flanges on both ends and the weld quality is decent. It is a pretty basic log manifold but it should be good enough for my purpose.
The turbocharger also looks decent at first glance.
In reply to Toyman! :
Nice! That little guy shouldn't hurt anything.
In reply to clutchsmoke :
I'm hoping it will work well around town in the lower to mid RPM range. I don't want something peaky that only makes power above 4500 RPM.
This is near the same size turbocharger I put on my 1970 Chevelle 25 years ago. It worked well on the 250 I6. The 3.7 is 225 ci so I think this will do what I need as long as I can get it tuned correctly.
If nothing else, it will be a learning experience and should be fun.
Worst case I screw it up and do an LS swap instead.
In reply to Toyman! :
i dig it! i don't know much about the atlas ECUs, are they comparable to the LS stuff of similar vintage and pretty easily tuneable?
If using the stock ecu, I'll be curious who you use to tune it and how good they are.
This is one of my concerns with adding a turbolater to the rx8.
In reply to budget_bandit :
They are tunable with HP Tuners. It uses an E67 ECU. My current ECU was tuned by PCM of NC and I have a spare that still has the factory tune on it. I will probably use the spare to tune for the turbocharger.
I have very limited experience with HP tuners. The only shop in town with an AWD dyno is a Subaru shop. I may end up tuning this myself.
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