STD Tuning Engine OM606 compound small turbo size

OM606 compound small turbo size

OM606 compound small turbo size

 
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atypicalguy
Holset

555
01-27-2019, 04:45 PM #6
There are many reasons to compound. Even the R2S setup used by Turbo came in varying configurations for different vehicles. Some required full compound for higher boost, some required earlier spool and were more sequential in operation. Running on the map of whatever turbos you are using is always smart of course. But you might choose to have the small turbo doing nothing at high rpm/horsepower, or you might choose to have it always in the mix.

So the desired power level and driving characteristics of the vehicle drive the turbo selection and function. Some may want good low end toque at low rpm. Some may care less about this.

For an OM606 to run higher hp ~400 at an AFR of 17:1, and not need 4 bar of boost to hit the air mass target, you will need an hx50 sized turbo. Personally I favor the hx52 "pro" model. It can supply the needed airflow at a moderate PR. Anything smaller will be boosting 4 bar at 80lb/minute, which is not what you really want in a compound. If you want 300hp then an hx40 will do the trick. The 40-sized turbos will make big power at lower AFR, but EGT will be high and they will smoke a lot before they come on line. Outfits like DPUK don't care about that stuff; they maintain the duty cycle is so low that the EGT doesn't matter, and they don't even tell you what it is when they sell you a kit. It is true that most street cars cannot put out maximum power for longer than a few seconds before breaking all sorts of laws and common sense.

But if you want earlier spool, little smoke, and good pull from low rpm, you need a vnt or compound. If compound, you can still use vnt, but not necessary. If not VNT, small turbo must be small to spool early.

Smaller turbo can be truly tiny. he221w, hx30 40mm/6cm, or even a stock om648 vnt Garrett. I would be tempted to try an he200wg 5cm, but it would only wake the big turbo and then go to sleep instantly. It might not spool an hx50 either. You can easily work this out in a spreadsheet taking into consideration compressor and intercooler efficiencies, and then plan the whole system and how much boost you need from the little turbo to light the large one.

You will need large bypass gates, one or two 60mm to keep backpressure down.

If you want to run full compound at all rpms, then you need a larger HP turbo. I think Sultzi had a nice 9cm HP turbine housing on a daily compound driver, so look up that build thread.
atypicalguy
01-27-2019, 04:45 PM #6

There are many reasons to compound. Even the R2S setup used by Turbo came in varying configurations for different vehicles. Some required full compound for higher boost, some required earlier spool and were more sequential in operation. Running on the map of whatever turbos you are using is always smart of course. But you might choose to have the small turbo doing nothing at high rpm/horsepower, or you might choose to have it always in the mix.

So the desired power level and driving characteristics of the vehicle drive the turbo selection and function. Some may want good low end toque at low rpm. Some may care less about this.

For an OM606 to run higher hp ~400 at an AFR of 17:1, and not need 4 bar of boost to hit the air mass target, you will need an hx50 sized turbo. Personally I favor the hx52 "pro" model. It can supply the needed airflow at a moderate PR. Anything smaller will be boosting 4 bar at 80lb/minute, which is not what you really want in a compound. If you want 300hp then an hx40 will do the trick. The 40-sized turbos will make big power at lower AFR, but EGT will be high and they will smoke a lot before they come on line. Outfits like DPUK don't care about that stuff; they maintain the duty cycle is so low that the EGT doesn't matter, and they don't even tell you what it is when they sell you a kit. It is true that most street cars cannot put out maximum power for longer than a few seconds before breaking all sorts of laws and common sense.

But if you want earlier spool, little smoke, and good pull from low rpm, you need a vnt or compound. If compound, you can still use vnt, but not necessary. If not VNT, small turbo must be small to spool early.

Smaller turbo can be truly tiny. he221w, hx30 40mm/6cm, or even a stock om648 vnt Garrett. I would be tempted to try an he200wg 5cm, but it would only wake the big turbo and then go to sleep instantly. It might not spool an hx50 either. You can easily work this out in a spreadsheet taking into consideration compressor and intercooler efficiencies, and then plan the whole system and how much boost you need from the little turbo to light the large one.

You will need large bypass gates, one or two 60mm to keep backpressure down.

If you want to run full compound at all rpms, then you need a larger HP turbo. I think Sultzi had a nice 9cm HP turbine housing on a daily compound driver, so look up that build thread.

 
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Messages In This Thread
OM606 compound small turbo size - by engineengineer - 01-20-2019, 08:43 PM
RE: OM606 compound small turbo size - by Turbo - 01-21-2019, 03:00 PM
RE: OM606 compound small turbo size - by firen456 - 01-22-2019, 03:15 AM
RE: OM606 compound small turbo size - by Turbo - 01-22-2019, 05:14 AM
RE: OM606 compound small turbo size - by firen456 - 01-22-2019, 07:07 AM
RE: OM606 compound small turbo size - by atypicalguy - 01-27-2019, 04:45 PM
RE: OM606 compound small turbo size - by barrote - 01-28-2019, 02:54 AM
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