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Optimal turbo setup
Om606STD Offline
Naturally-aspirated
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Posts: 5
Joined: Nov 2018
Location: United Arab Emirates
#1
Optimal turbo setup
Hi. I bought the Myna 8mm superpump 220cc and installed it on my OM606 with Garret turbo model GRW3476R 0.82 A/R delivering 3bar. This is producing 600-700whp. The car is 1998 G class automatic (722.6 gearbox from AMG55). Between 0 rpm and 3000 rpm there is big lag with huge amount of black smoke. It is dangerous for people driving behind me and getting me in trouble with police. How can I minimize the smoke without losing too much power? Is there a way I can control the pump like ECU? Do you think i should put 2 small turbos?
05-20-2019, 09:20 AM
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NZScott Offline
HX30W 73/44mm
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Posts: 378
Joined: Jul 2014
Location: New Zealand
#2
RE: Optimal turbo setup
Welcome to turbo lag. You need to adjust or fit an ALDA device which limits fuel until the boost comes up. There are even 2 stage ones now.

1978 300D, 373,000km
OM617.912 with a Holset HX30W, 7.5mm IP, 711.113 5 speed (awaiting certification to be legal...)

1977 250 270,000km (parts car)
1977 300D (ex 280) 500,000km 'new' DD





05-21-2019, 01:15 AM
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606110 Offline
K26-2
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Posts: 42
Joined: Jun 2017
Location: UK
#3
RE: Optimal turbo setup
700whp in a G class ? Do you mean Garrett GTW?
06-12-2019, 08:13 AM
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barrote Offline
Superturbo
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Posts: 1,558
Joined: Dec 2011
Location: Portugal
#4
RE: Optimal turbo setup
U're not making much sense...
But if u have 600hp very good u don't need anything . Just to control your foot.
FD,
Powered by tractor fuel
06-17-2019, 03:36 AM
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atypicalguy Offline
Holset
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Posts: 526
Joined: Oct 2013
Location: LA
#5
RE: Optimal turbo setup
Hi. I saw your post.

Great job with your setup. Sounds like you have a solid start to your project.

Basically, you have a lot to learn about setting up a mechanical diesel. These motors are really not used any more, but they are very reliable when set up correctly.

The problem is that you have to maintain the proper ratio of air to fuel at all rpm and loads. To make lots of HP, you need a large turbo that can compress a large amount of air very efficiently. This is because all motors tend to make more power with increasing rpm, up to a point. So your highest HP will come at high rpm, when the motor is using the most air and fuel.

If you get a turbo that size however, it will not work so well when the motor is at lower rpm. This is because the larger turbo requires a certain amount of exhaust to begin compressing air well, and you do not have that until higher rpm.

To solve this problem, you can do many things:
1. Decide you are happy with less peak power, and use a smaller turbo and less fuel. The smaller turbo will be much more responsive at low rpm, but will limit power at higher rpm because it cannot flow enough air.
2. Use a VNT turbo, which changes vane geometry at lower rpm to spool the turbo quickly, then modifies it at higher rpm to flow more exhaust.
3. Use a compound setup, where a small turbo and a large turbo are used together. The small turbo spools first and "lights" the large turbo.

For any of the above, you want the biggest intercooler(s) you can fit, and you want to be sure the air going into the motor comes from outside the vehicle - not under the hood.

You also want the biggest air filter you can fit, so that it does not choke the intake to the turbo.

But what you really need to do is some math.
1. Decide what your power output goal is, and at what rpm.
2. Decide what your target air fuel ratio is. For long engine life, I suggest 18 or 19:1. You can use 17, but your EGT will be hot and if anything goes wrong you run higher risk of melting a piston.
3. Decide on a BSFC. This is how much fuel the engine uses to make 1 hp. It changes with rpm. So figure out what rpm you are most interested in, and use that BSFC. It is determined by the engine design. There is a thread on om606 fueling over at 4btswaps that talks about it for the om606.
4. Pick a volumetric efficiency for the rpm you are interested in. It is also determined by the motor. It is basically a measure of pumping efficiency; how well air flows through the motor with each combustion cycle.
5. Pick an intercooler efficiency. 75% is very good. Be a bit conservative.
6. Pick a compressor efficiency for your turbo of choice. Keep in mind the turbo will not always run at peak efficiency. Max is usually ~75-78%
7. From the BSFC, figure out how much fuel you need to burn to make the power at the target rpm. Keep in mind the engine only injects every other cycle on a 4 stroke motor, so divide by 2. Keep in mind the density of diesel fuel; you need to convert from grams to cc to figure out how much volume the injection pump should inject. Since you already have the pump, you will likely just turn the fuel stop down until it stops smoking enough to suit your taste - whatever the turbo setup.
8. From the target fuel level, multiply by the target AFR to figure out how many grams of air you need to burn the target grams of fuel every cycle and then multiply by rpm/2. This gives your target air mass flow at target rpm.
9. Figure out how much you need to compress the air to fit that many grams of air into the engine with each combustion cycle. For this you need to know how many grams are in a liter of air at usual temp and pressure. Divide your target airflow mass by the number of grams in a liter at 1ATM, to get the target number of liters of air. Then divide this by the engine displacement, which is 3L. This gives you the desired Density Ratio to run at your target fuel level.
10. Adjust the target Density Ratio for VE and compressor and intercooler efficiencies. Basically, you have to oversize the turbo to provide the target airflow. This is a thermodynamics problem. The compressor introduces heat to the air beyond the work of compression (not 100% efficient). The intercooler similarly does not cool air all the way to ambient temp. There is a big thread called compound turbos 101 on 4bt swaps where Dougal and bush65 posted spreadsheets to help you with the math.
11. Pick a turbo that can efficiently provide the required adjusted Density Ratio at the required mass flow. You will need to look at some turbo maps. For a 606 at high fuel, you would likely need something like an hx52 at a PR of 3.5 to safely burn all the fuel you are putting into the motor. And a little VNT to run in compound with it to avoid the lag. erx000 setup, or similar. Custom exhaust manifold. Call pyry takkunen on instagram and have him make you one using the front clip off a gwagen and whatever turbos you select. Use two 60mm bypass gates for the vnt.
12. Invest in a good sensor setup, either the Banks iDash or an AEM CD-5 or CD-7 and put pressure and temp sensors everywhere. AEM have a CAN 25 module to allow expansion to suit. You can use a few and move them around, but you will need EGT and pressures before and after each turbo at a minimum. EGP before each turbo is a good idea also.

Ideally, you would drop the compression ratio by skimming the pistons, to keep peak cylinder pressures down and increase the lifespan of the motor. Cost effectiveness of this approach depends how many old om606 motors you have sitting around. Cutting it back to 13-17:1 will likely save you some grief.

The black smoke you have pouring out is a sign that your motor has far too much fuel and not enough air. This means high EGT and melting things if it goes on for more than a minute or two. So be careful. If the smoke clears at higher rpm that is a sign that airflow is adequate at higher rpm. This doesn't matter if the duty cycle is low; anywhere on a public road you will not be able to use this amount of power for more than a few seconds anyway. Smoke is more of a concern, as you mentioned. Offroad is another matter entirely, especially in the sand - the fuel ratio becomes more important. Or towing a trailer.

I have probably forgotten a bunch of stuff, but this should get you started. It is actually a pretty interesting set of concepts. Please keep in mind that I am not a trained engineer, and that this advice is worth exactly what you paid for it :-)
(This post was last modified: 06-29-2019, 11:16 AM by atypicalguy.)
06-29-2019, 11:10 AM
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