So, I'm debating what to do about an engine in my car...

E

embergloP51

Active member
So far, I'm thinking of either swapping in a 2jz from a supra or a 2.3 turbo from an SVO or possibly another engine such as a 4 banger from an EVO.

Tonight I started bouncing the idea around of twincharging the stock 200 I6. I think it could make for a really fun street motor and good for autocross/etc.

Does anybody have any experience with compound boost set ups? If I keep the 200, it will be fuel injected and run off a megasquirt for the best control over all the parameters and to hopefully avoid things like detonation.
 
Compound Turbo setups produce very high boost levels and are used mainly for diesel applications.
If you start adding wastegates and bypasses to keep the boost levels low, you lose the compound effect along with the system efficiency. The result is the same as using a single small turbo with a large wastegate.

So lets say you still want to pursue using compound turbos.
If you operate both of them at their minimum pressure ration of 1.5, that's a total multiplication of 2.25 atmospheres which is 33 PSI absolute or about 18 lbs of boost.

I've seen where a turbo is used to feed a supercharger for gasoline engines.
You get boost over a very wide rpm range and the turbo can use a higher turbine housing A/R than normal which increases overall efficiency.
 
pmuller9":1w990wyw said:
Compound Turbo setups produce very high boost levels and are used mainly for diesel applications.
If you start adding wastegates and bypasses to keep the boost levels low, you lose the compound effect along with the system efficiency. The result is the same as using a single small turbo with a large wastegate.

So lets say you still want to pursue using compound turbos.
If you operate both of them at their minimum pressure ration of 1.5, that's a total multiplication of 2.25 atmospheres which is 33 PSI absolute or about 18 lbs of boost.

I've seen where a turbo is used to feed a supercharger for gasoline engines.
You get boost over a very wide rpm range and the turbo can use a higher turbine housing A/R than normal which increases overall efficiency.
Click to expand...

Thanks for the input. Twin Charging is using a large turbo to feed a supercharger. 2 turbos would be a Twin Turbo set up.

I really don't see any disadvantage to twincharging as long as you can get it set up correctly and tuned well. I was hoping that somebody here had played with this type of system and had some insights about it.
 
embergloP51":20ljqd7e said:
I really don't see any disadvantage to twincharging as long as you can get it set up correctly and tuned well. I was hoping that somebody here had played with this type of system and had some insights about it.
Click to expand...
The roots supercharger and turbocharger combination works out well.
The supercharger adds low-end torque that replaces turbo lag and helps turbo spool time
while the turbo adds to the upper rpm supercharger boost and efficiency limitations. It is a good partnership.

Most DIY supercharger projects utilize the wrecking yard variety of used or rebuilt Eaton superchargers.
They are good for boost levels up to 8 to 10 lbs. Much past that they run too hot and detonation becomes a problem.

These units also do not reach their max volumetric efficiency until a certain rpm.
If a lot of boost is needed at very low rpm then the rule is to use a smaller supercharger and spin it faster to achieve desired boost levels. The problem here is, at high engine rpm, the supercharger rpm is too high and it runs hot once again.

Let’s say the goal is 15 lbs of boost
One plan is to run the supercharger at a comfortable 6 to 7 lbs of boost and have the turbo feed the throttle body at the inlet of the charger to add the additional boost. The turbo can easily utilize an intercooler between it and the charger which reduces the heat, increases efficiency and reduces detonation.
At low rpm, WOT will give you 6 to 7 lbs instantly and the turbo will quickly spool the extra 8 lbs where the wastegate will regulate at that point. You still reference the wastgate controller off the intake manifold for total boost which is 15 in this case.

The turbo is sized according to the supercharger flow rate.
At 7 lbs of boost the charger is pumping about 45% more air by weight than the engine so the turbo will be larger to match

Plan 2 is more complicated.
Most of the chargers have a bypass valve that is used during no boost conditions like cruising where it opens the charger inlet to the outlet letting the charger recirculate air through itself instead of pumping into the engine.
This drops the drive power to very little and the recirculating air cools the charger.

When the throttle is snapped to wide open and the turbo is just idling the charger supplies boost and there is a vacuum at the inlet of the charger. As the turbo spools the charger inlet transitions from a vacuum to pressure. At that point the turbo is pumping more than the charger. Once the inlet side sees a pressure, you can use the pressure to control the bypass valve and begin opening.
Once the bypass is fully opened, the charger is bypassed and the turbo is supplying all of the pressure.
The charger only needs a small amount of power to drive it and the air is not being re-heated by the charger after being intercooled.

In this second case the turbo will be sized according the engine airflow rate since the charger is bypassed at upper boost levels and will be smaller than the previous case.

The alternative to all of this is to hurt your wallet and use one of the following instead without the turbocharger.
Eaton TVS, Whipple or Kenne Bell superchargers.
 
pmuller9":3m13ziq6 said:
embergloP51":3m13ziq6 said:
I really don't see any disadvantage to twincharging as long as you can get it set up correctly and tuned well. I was hoping that somebody here had played with this type of system and had some insights about it.
Click to expand...
The roots supercharger and turbocharger combination works out well.
The supercharger adds low-end torque that replaces turbo lag and helps turbo spool time
while the turbo adds to the upper rpm supercharger boost and efficiency limitations. It is a good partnership.

Most DIY supercharger projects utilize the wrecking yard variety of used or rebuilt Eaton superchargers.
They are good for boost levels up to 8 to 10 lbs. Much past that they run too hot and detonation becomes a problem.

These units also do not reach their max volumetric efficiency until a certain rpm.
If a lot of boost is needed at very low rpm then the rule is to use a smaller supercharger and spin it faster to achieve desired boost levels. The problem here is, at high engine rpm, the supercharger rpm is too high and it runs hot once again.

Let’s say the goal is 15 lbs of boost
One plan is to run the supercharger at a comfortable 6 to 7 lbs of boost and have the turbo feed the throttle body at the inlet of the charger to add the additional boost. The turbo can easily utilize an intercooler between it and the charger which reduces the heat, increases efficiency and reduces detonation.
At low rpm, WOT will give you 6 to 7 lbs instantly and the turbo will quickly spool the extra 8 lbs where the wastegate will regulate at that point. You still reference the wastgate controller off the intake manifold for total boost which is 15 in this case.

The turbo is sized according to the supercharger flow rate.
At 7 lbs of boost the charger is pumping about 45% more air by weight than the engine so the turbo will be larger to match

Plan 2 is more complicated.
Most of the chargers have a bypass valve that is used during no boost conditions like cruising where it opens the charger inlet to the outlet letting the charger recirculate air through itself instead of pumping into the engine.
This drops the drive power to very little and the recirculating air cools the charger.

When the throttle is snapped to wide open and the turbo is just idling the charger supplies boost and there is a vacuum at the inlet of the charger. As the turbo spools the charger inlet transitions from a vacuum to pressure. At that point the turbo is pumping more than the charger. Once the inlet side sees a pressure, you can use the pressure to control the bypass valve and begin opening.
Once the bypass is fully opened, the charger is bypassed and the turbo is supplying all of the pressure.
The charger only needs a small amount of power to drive it and the air is not being re-heated by the charger after being intercooled.

In this second case the turbo will be sized according the engine airflow rate since the charger is bypassed at upper boost levels and will be smaller than the previous case.

The alternative to all of this is to hurt your wallet and use one of the following instead without the turbocharger.
Eaton TVS, Whipple or Kenne Bell superchargers.
Click to expand...

Thank you much! The plan is an eaton m90 and a turbo that is on the large side for a motor. Probably end up running 20lbs of boost in the manifold. I'd love to give this a shot. It'll probably be a slow build starting by just turboing the car then figuring out how to add in the supercharger.

Super4ord, It's a 66 Mustang Coupe.
 
embergloP51":24q4x5q2 said:
Thank you much! The plan is an eaton m90 and a turbo that is on the large side for a motor. Probably end up running 20lbs of boost in the manifold. I'd love to give this a shot. It'll probably be a slow build starting by just turboing the car then figuring out how to add in the supercharger.
Super4ord, It's a 66 Mustang Coupe.
Click to expand...
Don't forget that the turbo is sized for the supercharger airflow and it will be too large to use with engine only.

You will need to install the M90 first and getting it sorted out.
Supercharger installation is more difficult on these engines than a turbo and you will need the charger in first anyway to figure out the turbo and intercooler installation.

I would start with close to a 1.5:1 drive ratio.
Depending on the cylinder head, cam combination it should get you around 7 to 8 lbs of manifold pressure.

Are you doing any head porting?
What RPM are you expecting to run this engine at?
What size turbo do you have? (Compressor Inducer or inlet diameter)
 
pmuller9":20kcslwi said:
embergloP51":20kcslwi said:
Thank you much! The plan is an eaton m90 and a turbo that is on the large side for a motor. Probably end up running 20lbs of boost in the manifold. I'd love to give this a shot. It'll probably be a slow build starting by just turboing the car then figuring out how to add in the supercharger.
Super4ord, It's a 66 Mustang Coupe.
Click to expand...
Don't forget that the turbo is sized for the supercharger airflow and it will be too large to use with engine only.

You will need to install the M90 first and getting it sorted out.
Supercharger installation is more difficult on these engines than a turbo and you will need the charger in first anyway to figure out the turbo and intercooler installation.

I would start with close to a 1.5:1 drive ratio.
Depending on the cylinder head, cam combination it should get you around 7 to 8 lbs of manifold pressure.

Are you doing any head porting?
What RPM are you expecting to run this engine at?
What size turbo do you have? (Compressor Inducer or inlet diameter)
Click to expand...


Interesting. I'll keep that in mind.

Is there any reason not to intercool the M90? I've heard they are small for these motors and can overheat? Although if I swap in a 4 cylinder I don't think that will be so important?

I was figuring on the stock pulleys and drive ratio. I would probably want no more than 8lbs from each source of boost.

If I keep the 200, it will get the Classic Inlines head with a megasquirt system. Under 6k rpm probably. Haven't bought the turbo yet. I need to figure out the airflow numbers.
 
embergloP51":37vf42do said:
Is there any reason not to intercool the M90? I've heard they are small for these motors and can overheat? Although if I swap in a 4 cylinder I don't think that will be so important?

I was figuring on the stock pulleys and drive ratio. I would probably want no more than 8lbs from each source of boost.

If I keep the 200, it will get the Classic Inlines head with a megasquirt system. Under 6k rpm probably. Haven't bought the turbo yet. I need to figure out the airflow numbers.
Click to expand...

Most of the M90s were used on the GM 231 cid V6s so a 200 six is a good match.
At 8 lbs of boost and supercharger rpm under 8000, the temp air rise is about 120* F.
A water to air intercooler is normally used for a supercharger.

The turbocharger will need to be intercooled because you don't want to feed the M90 with hot air.
That can be an air to air intercooler.

What size pulley is on your M90?
 
I designed the first variable geometry turbine turbo. Dont know what Borg Warner did with it after bying out Schwitzer or what sizes they build but it could be diled in to provide boost at idle. It could act as a small turbo for fast boost build up like a small turbo then open vanes up and act like a large turbo.
 
Thanks guys for the input. Twincharging is definitely something I want to try, but probably after I have a 2nd car so I have something to drive while sorting it out. For now I'll probably use a china-charger and see how I like that.
 
turbo2256b":15nhlhgt said:
I designed the first variable geometry turbine turbo. Dont know what Borg Warner did with it after bying out Schwitzer or what sizes they build but it could be diled in to provide boost at idle. It could act as a small turbo for fast boost build up like a small turbo then open vanes up and act like a large turbo.
Click to expand...
I've got a Garret VGT on my 6.0 PSD. I monitor it with an app called Torque on a spare Android phone. Two of the PIDs I monitor are the VGT% and the throttle position, you can watch it close up the exhaust side while at idle and how far it opens when its under boost, its a fun thing to observe. You would need quite the controller to get it working properly.

But if somebody ever does get on the path for this type of installation, look at the 'new' 6.7L Powerstroke turbo. 1 exhaust side with a common shaft two two different sized compressors. Small for low speed and it transitions to the larger for higher boost.
 
CoupeBoy":10h8092g said:
turbo2256b":10h8092g said:
But if somebody ever does get on the path for this type of installation, look at the 'new' 6.7L Powerstroke turbo. 1 exhaust side with a common shaft two two different sized compressors. Small for low speed and it transitions to the larger for higher boost.
Click to expand...
Click to expand...

Damn. That powerstroke turbo sounds awesome. I'll have to look that up.
 
That's kind of what I was thinking, but using the supercharger to feed the turbo with precompressed air. It multiplies the boost factor and will help bypass the turbo's lag. Which in theory will allow you to run a much larger turbo than you would on a stock motor. Basically just like a twin turbo set up, but using a supercharger as the smaller first turbo.

Sorry for the long delay. I was in a crash in the Mustang. Over the last few months I've been concentrated on getting her repainted and fixed up. Even better than she was before now.
 
Thanks Jack.

There's a couple of local tuner shops with great reputations for turbo installs. I bet they could build me a great manifold. I'll have to get a quote. Man, if I built this car exactly how I wanted, it would be crazy expensive. haha
 
embergloP51":cj4erf3f said:
That's kind of what I was thinking, but using the supercharger to feed the turbo with precompressed air. It multiplies the boost factor and will help bypass the turbo's lag.
Click to expand...

An M90 is a positive displacement pump rated at 90 cu. inches per revolution and that is all the airflow it will allow by volume. Anything after the supercharger will be restricted to that airflow limit including a turbocharger.
In order to change max boost, the supercharger drive ratio would need to be changed or the supercharger would need to be bypassed at some point and let the turbo wastegate control max boost.
If the supercharger is not bypassed the wastegate controls the pressure ratio shared between the charger and the turbo.
Once the turbo is operating at the pressure ratio needed for full boost and the supercharger is at a 1:1 pressure ratio, if the waste gate continues to drive the turbine, the turbo can be driven into the surge zone and over rev. This is again because the supercharger is restricting the turbo inlet flow. Wastegate settings are critical with this configuration.

The turbocharger is a centrifugal pump (not positive displacement) that is not mechanically connected to the engine.
The supercharger can draw through the turbo with very little restriction until the turbo begins pumping more volume than the supercharger.
Then the turbo is feeding the supercharger with compressed air and the supercharger flows more air by weight at a set volume/rev.
With this configuration the wastegate operates normally and you can vary max boost with the wastegate.

The turbo is sized according to the airflow of the supercharger and will be larger than sizing it by the engine displacement and rpm.
 
Thats right. A compound system (by semantics) is a turbo charger with auxilary propolsion as per some diesel trucks.

What is being discussed here is a Lancia Delta S4 combination system See https://en.wikipedia.org/wiki/Twincharger.

You can upsize the base turbo by an ALS (Anti Lag System) https://en.wikipedia.org/wiki/Antilag_system. David Vizard cottoned on to it in the late 70's, Keith Duckworth of Cosworth described Ferraris 120 degree V6 F1 engine with downstream injectors into the exhaust pipe as an ALS system as a "conventional piston engine sharing is combustion chamber with a jet turbine engine".

The key is sizing the turbo and supercharger.

Before Group B got scrapped by FISA when FIAT were found cheating, the engines were oven symetrically designed for a both. Very good idea here.
 
FWIW, VW has a twincharged (super+turbo) system in production today, although it's slated to be killed.

VW_twincharged.jpg


You can see their solution is a valve which bypasses the supercharger and a clutch which disengages it once the turbo is up to speed. That way it isn't dead weight through half the rev range. :)
 
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