Twin-Turbo 2011 Mustang GT Makes 791 RWHP!
01-08-2012, 02:21 AM
#11
The problem with turbo aftermarket kits is matching the turbo kits to the specific engine, assuming stock intake, exhaust, cams, and all the other stuff that deal with flowing the fresh intake and exhaust gases.
Usually, factory turbos on cars that come stock with them are matched precisely to the car. the right turbine and compressor wheel diameters, the right banjo housing dimensions, the right vane design, the right variable vanes for variable turbos, etc.
There are aftermarket turbo kits out there on the market and some of them honestly are a "one size fits all" approach, meaning that the company probably just quickly threw a kit together and did not design the kit form the ground up with the engine it is meant to go on.
Lag occurs from a turbo that is too big for the engine in question or the vanes, banjo housings,etc are not properly designed to exploit the exhaust gases properly to mitigate/eliminate the lag.
Tuning can only go so far to mitigate a mismatch, so it becomes imperative to find a good aftermarket company that designs each kit specifically for the car in question.
For me, I personally would prefer turbos over a mechanically coupled supercharger because of the lack of loss of mechanical energy to turn the compressor.
And turbos are completely variable independent of the crank, so you do not have to worry about having a supercharger rotor speed indexed to the crank RPM. I.e. at lower RPMs, and light throttle applications, the turbo speed is slow and speeds up only as exhaust gases hit the turbine vanes. At full throttle applications, when the engine is accelerating much faster, assuming the right size turbos for the engine, the turbos speed up at a more proper speed curve in relation to the crank, but again independent of the crank.
But of curse, the trubos not being mechanically coupled to the crank is also its disadvantage for a mismatched turbo for the engine in question. You get lag in a mismatched situation where the turbos do not speed up fast enough.
During WW2, fighter airplane superchargers were variable speed, well, two speed. By variable speed supercharger, I mean that the compressor has two pullies:
One pulley is set for low altitude applications.
The other pulley of a different diameter is set for high altitude applications where you need more boost.
Modern automotive superchargers do not have such an advantage. It is only one pulley size and you are stuck with it. You physically have to take off the serpentine belt and dismount the old pulley and bolt on a different one to change your boost level.
Now, some modern cars do have a supercharger clutch, a la Mad Max. In light throttle applications where you do not need boost, the clutch disengages the supercharger so you do not lose mechanical energy to turn the rotors. When you need boost, the clutch engages and the lobes start to turn.
To prevent the lobes from becoming a pump engine that draws away more energy, these deactivating superchargers have a bypass valve which re-routes the fresh intake air to completely detour around the lobes and not have to be forced through the lobes.
Turbos have the advantage of not needing to do this, the energy to turn them is made up by the energy they help create by upping the boost.
But I guess a similar bypass system can be devised such that the intake air and exhaust gases do not even go to the turbos when boosting is completely not necessary. But that only adds more to the plumbing complications that turbos already inherently create.
Usually, factory turbos on cars that come stock with them are matched precisely to the car. the right turbine and compressor wheel diameters, the right banjo housing dimensions, the right vane design, the right variable vanes for variable turbos, etc.
There are aftermarket turbo kits out there on the market and some of them honestly are a "one size fits all" approach, meaning that the company probably just quickly threw a kit together and did not design the kit form the ground up with the engine it is meant to go on.
Lag occurs from a turbo that is too big for the engine in question or the vanes, banjo housings,etc are not properly designed to exploit the exhaust gases properly to mitigate/eliminate the lag.
Tuning can only go so far to mitigate a mismatch, so it becomes imperative to find a good aftermarket company that designs each kit specifically for the car in question.
For me, I personally would prefer turbos over a mechanically coupled supercharger because of the lack of loss of mechanical energy to turn the compressor.
And turbos are completely variable independent of the crank, so you do not have to worry about having a supercharger rotor speed indexed to the crank RPM. I.e. at lower RPMs, and light throttle applications, the turbo speed is slow and speeds up only as exhaust gases hit the turbine vanes. At full throttle applications, when the engine is accelerating much faster, assuming the right size turbos for the engine, the turbos speed up at a more proper speed curve in relation to the crank, but again independent of the crank.
But of curse, the trubos not being mechanically coupled to the crank is also its disadvantage for a mismatched turbo for the engine in question. You get lag in a mismatched situation where the turbos do not speed up fast enough.
During WW2, fighter airplane superchargers were variable speed, well, two speed. By variable speed supercharger, I mean that the compressor has two pullies:
One pulley is set for low altitude applications.
The other pulley of a different diameter is set for high altitude applications where you need more boost.
Modern automotive superchargers do not have such an advantage. It is only one pulley size and you are stuck with it. You physically have to take off the serpentine belt and dismount the old pulley and bolt on a different one to change your boost level.
Now, some modern cars do have a supercharger clutch, a la Mad Max. In light throttle applications where you do not need boost, the clutch disengages the supercharger so you do not lose mechanical energy to turn the rotors. When you need boost, the clutch engages and the lobes start to turn.
To prevent the lobes from becoming a pump engine that draws away more energy, these deactivating superchargers have a bypass valve which re-routes the fresh intake air to completely detour around the lobes and not have to be forced through the lobes.
Turbos have the advantage of not needing to do this, the energy to turn them is made up by the energy they help create by upping the boost.
But I guess a similar bypass system can be devised such that the intake air and exhaust gases do not even go to the turbos when boosting is completely not necessary. But that only adds more to the plumbing complications that turbos already inherently create.
01-10-2012, 09:55 AM
#13
1st Gear Member
Join Date: Dec 2011
Location: Florida
Posts: 72
Jim,
Good post and I agree. We spent a lot of time considering the design of this kit and it really shows when you drive the car.
I do need a correction made in the story on the homepage though if anyone knows who to get in touch with. I used to own Modular Depot but moved to South Florida 2 years ago. This project is being done by myself, Jake Long and Jon Lund and doesn't have anything to do with MD. Just wanted to clear that up.
Ken
Good post and I agree. We spent a lot of time considering the design of this kit and it really shows when you drive the car.
I do need a correction made in the story on the homepage though if anyone knows who to get in touch with. I used to own Modular Depot but moved to South Florida 2 years ago. This project is being done by myself, Jake Long and Jon Lund and doesn't have anything to do with MD. Just wanted to clear that up.
Ken
01-11-2012, 06:35 PM
#15
Regardless, those guys are sharp. They'll have it fixed up and in the 9s in the blink of an eye.
01-11-2012, 11:04 PM
#16
1st Gear Member
Join Date: Dec 2011
Location: Florida
Posts: 72
I wouldn't say it blew up. It broke the oil pump. This has happened on quite a few of these cars. Livernois had their oil pump go on a naturally aspirated car. Either way, instead of fixing it and probably breaking something else, we are doing an all out build on it. The new engine should be done in less than 2 weeks.
We will continue stock engine development on the next car we do. But from here on out, any car we plan to push very hard, we are going to put billet oil pump gears in for safety. Out of all the 9 second 5.0s I know of, over half have had oil pump failures. The billet gears are cheap insurance.
We will continue stock engine development on the next car we do. But from here on out, any car we plan to push very hard, we are going to put billet oil pump gears in for safety. Out of all the 9 second 5.0s I know of, over half have had oil pump failures. The billet gears are cheap insurance.
01-11-2012, 11:20 PM
#18
1st Gear Member
Join Date: Dec 2011
Location: Florida
Posts: 72
We will find out on the next car we do as long as the owner wants to push it. If not, we will eventually get back there with a stock engine. We will just put the billet pump in. Just as a science experiment.
The oil pump didn't just break from power. It's hard to say what does it. The theory on all the other cars was the load from the belt because they were all supercharged. But obviously that was not our problem. It's possible detonation cracked it. I didn't lose oil pressure until after I lifted. Which makes me think it cracked/broke somewhere during the pass but was still making pressure. Then when I lifted and took the load off of it, it broke all the way and I lost pressure.
I also blew through the 1-2 shift on that pass and hit the limiter super hard at 7,800. But I've done that on other cars quite a bit with no issue.
01-12-2012, 01:10 AM
#19
1st Gear Member
Join Date: Dec 2011
Location: Florida
Posts: 72
It certainly is for stock internals, very nice.
I've always wondered why there was less turboing vs SC's with Mustangs. Only thing I can come up with is that the linear power of a SC fits better with an already powerful engine vs a turbo's upper (generally) RPM power gains - just a theory.
That is one naughty Mustang, MMM MMmmm..
I've always wondered why there was less turboing vs SC's with Mustangs. Only thing I can come up with is that the linear power of a SC fits better with an already powerful engine vs a turbo's upper (generally) RPM power gains - just a theory.
That is one naughty Mustang, MMM MMmmm..
01-12-2012, 09:39 AM
#20
Speaking of the stock oil pump failing, I don't know if it has any bearing, but would the Boss 302 oil cooler possibly help? I know that does not address the salient hardware (the pump gears), but my guess here is reducing the oil temp might help relieve some stress.
Additionally, possible switching the Boss 302 oil pump in? That is, if the Boss 302 oil pump is even upgraded over the Coyote oil pump. Afterall, the Boss 302 is designed to run at 7500RPM redline, at which speeds the oil pump no doubt is working harder.
Additionally, possible switching the Boss 302 oil pump in? That is, if the Boss 302 oil pump is even upgraded over the Coyote oil pump. Afterall, the Boss 302 is designed to run at 7500RPM redline, at which speeds the oil pump no doubt is working harder.