When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I also see online a lot of guys are dumping converter pressure to stall higher to build boost on the brake. I've never tried it nor have I personally known anyone to try it, but it makes sense. Might want to investigate that as well.
interesting, as I find that to be the least attractive characteristic of the EFR(s).
It makes packaging more difficult but it makes the bearing arrangement more robust. I can deal with the tiny extra length of the bearing housings for fitting it places.
I ordered some cams just now. Still thinking about whether I will pick up that Xona Rotor turbo. It's a lot bigger than the EFR 7670, so spool is probably going to be poor. Would need to copy Newaza's compressed air setup for sure to get some good spool characteristics. But I want to do that anyways, so this bigger turbo would just force the issue.
Thats a pretty short bearing housing. I think I'd rather have the longer spacing between bearings that the EFR has to offer.
Well that makes sense. I could definitely see that being a pro for bearing life from improved support. I had not even noticed the difference until you pointed that out.
My big concern is pushing an EFR too hard and breaking it. It seems turbos with conventional inconel parts are more durable to high RPM and general abuse than the EFRs. From talking to full race, they don't recommend taking the 7670 beyond 120k rpm, even though it's rated to go to 140k.
Well that makes sense. I could definitely see that being a pro for bearing life from improved support. I had not even noticed the difference until you pointed that out.
My big concern is pushing an EFR too hard and breaking it. It seems turbos with conventional inconel parts are more durable to high RPM and general abuse than the EFRs. From talking to full race, they don't recommend taking the 7670 beyond 120k rpm, even though it's rated to go to 140k.
Yeah but its an EFR so for the same boost threshold as any other turbo you will make more power. IE if you pick the biggest EFR thats on full boil by 4k rpms it'll make more power than anything else you can buy so you dont actually have to push it as hard.
Yeah but its an EFR so for the same boost threshold as any other turbo you will make more power. IE if you pick the biggest EFR thats on full boil by 4k rpms it'll make more power than anything else you can buy so you dont actually have to push it as hard.
Took a while to reply, but I keep thinking about this. You're technically right. I had not, but should have thought of it that way.
Moving on, I haven't bought a new turbo yet. Been bouncing around a lot of different ideas for a future setup. The immediate plan hasn't changed, EFR7670 and go. But long term, I do think a new setup will be built and tested.
One consideration is another compound setup. One possibility is to have the 1.6L whipple coldside, with a manifold similar to FFS, (no intercooler, but E85 only), and a traditional turbo on the hotside. The hard part of this is getting the blower installed and building a setup that addresses every known issue I had with the previous blower setup. Upside is I don't have the complexity of a twincharged setup with valves, control systems, complex piping, etc.
Or possibly a compound turbo setup with both turbos in the engine bay. No idea how that would package, like hell is my guess. Haven't done much on this, but it's an obvious possibility for a compound setup.
FWIW, the only reason to do any compound setup would be to improve the torque curve at low and mid range. I can buy a turbo that will make the top end power no problem, but those turbos will be lacking on the low end.
I think the whipple and large turbo would produce the most fun-to-drive setup. So leaning that direction.
Please, please just try the big EFR you ALREADY have first.
I've always thought "what if Pat put his ingenuity into a decent single turbo, I'd bet he would be faster and have less teething problems."
If it's punky down low then "Newza" it or feed it a bit of nitrous.
Please let us see what simple does first, the above is the simple
I think the whipple and large turbo would produce the most fun-to-drive setup. So leaning that direction.
Definitely have to agree with that, I have built several of those over the years on various cars with great success.
Suggest you mount your blower down low on the hot side, below the turbo. It helps a LOT with keeping blower case temperatures within reason, and allows any amount of intercooling.
Mocking up a GT3582 over a front entry TVS1320 on the engine stand right now in fact.
Another tip is buy real Sanden or Denso compressors (ac compressors)
If you cannot find one inexpensively give me a call and I'll hook you up.
You should have my number deep in your phone.
There is NO such thing as a "rebuilt" compressor.
All rebuilds are simply re-seals and YOU can handle a compressor re-seal yourself.
The compressor are made out of hyper-eutectic aluminum and are not machinable.
NO internal parts are available...
Only choice is new Chinese (sucks donkey *****) or new OEM which is commonly Sanden or Denso.
They work fine.
Please, please just try the big EFR you ALREADY have first.
I've always thought "what if Pat put his ingenuity into a decent single turbo, I'd bet he would be faster and have less teething problems."
If it's punky down low then "Newza" it or feed it a bit of nitrous.
Please let us see what simple does first, the above is the simple
The EFR is going on first, don't worry. I'm skeptical of how much power it can make, but maybe I'm wrong and it's more capable than I think.
Originally Posted by Warpspeed
Definitely have to agree with that, I have built several of those over the years on various cars with great success.
Suggest you mount your blower down low on the hot side, below the turbo. It helps a LOT with keeping blower case temperatures within reason, and allows any amount of intercooling.
Mocking up a GT3582 over a front entry TVS1320 on the engine stand right now in fact.
We need to talk! I'd love to ask you some questions relating to your experience with these setups.
Originally Posted by technicalninja
Another tip is buy real Sanden or Denso compressors (ac compressors)
If you cannot find one inexpensively give me a call and I'll hook you up.
You should have my number deep in your phone.
There is NO such thing as a "rebuilt" compressor.
All rebuilds are simply re-seals and YOU can handle a compressor re-seal yourself.
The compressor are made out of hyper-eutectic aluminum and are not machinable.
NO internal parts are available...
Only choice is new Chinese (sucks donkey *****) or new OEM which is commonly Sanden or Denso.
They work fine.
I'll shoot you a PM, but not sure if I have your number. But I'd be interested in getting a good compressor. I had previously been looking at the cheap Chinese ones for about 140 bucks or so. I've used cheap ones in the past, and my experience has been that some were ok, but many didn't perform as good as the original.
We need to talk! I'd love to ask you some questions relating to your experience with these setups.
I built my first compound system over thirty years ago, all the problems have been solved.
Much better than either just a supercharger or just a turbo by itself.
You get the advantages of both without any of the disadvantages of either.
The biggest advantage is that you can keep boost pressure way above turbine inlet pressure over the entire engine operating range for really efficient scavenging and heat removal from the combustion chamber. That seriously raises the detonation threshold and you can really pack cool dense charge into the cylinder unhindered by red hot exhaust residuals.
Any positive displacement supercharger suffers from falling volumetric efficiency above the highest efficiency point on the map, turning it faster is not a solution, it only makes things worse.
The fix for that is a really large turbo running at an unusually low pressure ratio to fill the supercharger rotors with increasing engine rpm.
You do not need to thrash either the blower or the turbo, both can operate at relatively low pressure ratios in the most efficient part of their operating range.
A turbo that is at full boost at only maybe 4psi will spool instantly and have a very low boost threshold. A big compressor can shift a lot of air at low compressor rpm, and the turbine power to drive it will be minimal. Inertia is proportional to the square of rpm, so it spools pretty much instantly.
Not only that, the exhaust turbine gets ALL of the exhaust energy, the turbo compressor does only perhaps a third of the work of compression. So spool is pretty explosive and instant.
The supercharger multiplies the engine capacity as far as the turbo goes. A 1.9 litre engine looks like a 3.5 litre engine to the turbo. It does not "know" there is a supercharger there.
Turbo performance, even a very very large turbo will amaze you how responsive it can be if you only expect low boost from it.
I built my first compound system over thirty years ago, all the problems have been solved.
Much better than either just a supercharger or just a turbo by itself.
You get the advantages of both without any of the disadvantages of either.
The biggest advantage is that you can keep boost pressure way above turbine inlet pressure over the entire engine operating range for really efficient scavenging and heat removal from the combustion chamber. That seriously raises the detonation threshold and you can really pack cool dense charge into the cylinder unhindered by red hot exhaust residuals.
Any positive displacement supercharger suffers from falling volumetric efficiency above the highest efficiency point on the map, turning it faster is not a solution, it only makes things worse.
The fix for that is a really large turbo running at an unusually low pressure ratio to fill the supercharger rotors with increasing engine rpm.
You do not need to thrash either the blower or the turbo, both can operate at relatively low pressure ratios in the most efficient part of their operating range.
A turbo that is at full boost at only maybe 4psi will spool instantly and have a very low boost threshold. A big compressor can shift a lot of air at low compressor rpm, and the turbine power to drive it will be minimal. Inertia is proportional to the square of rpm, so it spools pretty much instantly.
Not only that, the exhaust turbine gets ALL of the exhaust energy, the turbo compressor does only perhaps a third of the work of compression. So spool is pretty explosive and instant.
The supercharger multiplies the engine capacity as far as the turbo goes. A 1.9 litre engine looks like a 3.5 litre engine to the turbo. It does not "know" there is a supercharger there.
Turbo performance, even a very very large turbo will amaze you how responsive it can be if you only expect low boost from it.
Ask away....
Ha, someone who actually has his **** together, I basically agree with all of the above with one exception...
If you can find the "perfect" turbo for your application the turbine inlet pressure (TIP) will be LOWER than the compressor exit pressure (boost) and all that wonderful clearing of the exhaust gasses will occur without the added complexity and weight of the supercharger.
This is why I've always thought a properly sized single is the "best (or maybe simplest)" way to go on anything under 2.5L displacement.
No one ever talks about their TIP/Boost ratio and it is one of the most important numbers.
Go below 1 and everything gets better.
Feed the turbo from a high pressure area on the car (maybe just above the splitter) and this is easier to achieve. This high pressure source gains pressure the faster you go...
Now Warpspeed's set up will make boost earlier than a single but do you really need 10psi at 1500 rpm...
It wouldn't surprise me if one of his problems has been too much boost too soon.
This was one of Corky Bell's problems with the Aero-dyne variable aspect ratio turbos of the late 80s - early 90s. He had to reduce the turbos output down low.
The Aero-dyne always had a TIP/Boost ratio below 1. It turned out to not be reliable but...
It also had NO oiling system, no feed, no drain. It had a small reservoir of space age lubricant that you occasionally had to fill. Made turbo installation easier.
Now, first thing I did after seeing Warpspeeds post was to check his page. He's 70 years old!
You should ALWAYS respect your elders, especially elders who know what they are talking about...
I will now watch for Warpspeed posts as he is worth listening to...
I also listen to Corky as well. His engineering advice was always top shelf.
Haha, I am 70 years old as well.
Anyhow, you are quite right about the advantages of keeping boost pressure well above turbine inlet pressure, and as turbo technology continues to improve, that is becoming more possible and easier to do.
But it still requires a pretty large turbo, and that certainly impacts boost threshold.
Now its definitely also true that when you are in a hurry, the engine may never see the region below 4,000 rpm, so a really big fat turbo can be real fun flat out.
But if you drive it to work every day through dense bumper to bumper traffic, the engine is more likely to be in the 2,000 to 3,000 range, and its nice to have at least a little bit of usable torque down there.
That does not necessarily make it any faster, just a lot easier and a lot more pleasant to drive.
High boost down low is less of a problem if the compression ratio is made sensibly lower, and the flywheel heavier. Jaguar discovered when they first started supercharging their engines a much heavier flywheel makes a big difference to torsional fluctuations and smoothness in the drivetrain, and its much worse with fewer cylinders.
A supercharger will act as a quite effective torsional damper at the front of the engine, the blower rotors and drive have mass, and the drive belt makes an elastic damper.
Now many people condemn low compression ratios, and it certainly makes the engine more fuel hungry at light throttle. But one aspect most people miss, is that a much larger combustion space can pack a larger volume of fuel/air, and the EXPANSION ratio of that is lower (low compression ratio = low expansion ratio) and it pushes harder and longer during the power stroke.
The second disadvantage of a low compression ratio is poorer theoretical exhaust scavenging. More trapped exhaust residuals in the unswept volume. But with a supercharger and even a small amount of valve overlap, scavenging or exhaust reversion is never a problem at any rpm.
Too many people try to run too high a compression ratio, then have to back off the ignition when it starts to rattle with detonation. Its definitely possible to build a smooth torque monster that also has a lot of top end power, if the whole thing is thought right through and properly planned.
A low compression turbo engine really impacts spool. "If it ain't makin low end torque, its got no exhaust flow to drive the turbine"
Add a positive displacement supercharger between the turbo and the engine, spool problem completely solved.
I am probably the first person to fit a TVS1320 to a Miata, they are freakin ENORMOUS.
This is still just an engine stand mock up, but it all definitely fits.
Some junk blower mounts to get the TVS1320 positioned parallel to the crank.
Had to raise the power steering pump and lower the aircon compressor to make room. Definitely an interesting packaging exercise, but it has all worked out rather well.
From the back.
Kraken turbo manifold and external wastegate for the cheap Chinese fake GTR3582. I bought that plus three turbine housings for a quarter the cost of a genuine Garrett. Its rubbish, but it is identical in size to the real thing, so perfect for an initial mock up. Should be able to establish required exhaust housing A/R from road testing, then order a real turbo. Don't take fright at the mild steel all thread holding the turbo.
Side view.
And no, the supercharger is not blowing back into the turbo exhaust its an optical illusion haha !
Definitely don't want to hijack Pat's thread, but he did show some interest.
I will shut up at this point.
Hey, feel free to post every pic you have of your setups! I'd love to see them. Not many people building these, or have run them in the past. Really any info is appreciated.
With my current automatic and converter, I could support a healthy size turbo if I had the SC adding boost, as I think I can probably slip the converter up to about 4,500 RPM or so if I had 15 PSI boost from a blower. That would help light off almost any turbo probably.
11-20-2020, 09:10 PM
0
