Single or Twin Turbo?
- Thread starter Red9
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Hey Red9,
To answer your question om which is better single or twin is a bit hard to answer without more info. (budget, room, purpose of car etc). I've read that Porshe has done some resarch into the matter and has concluded that if the turbos are appropriately sized, then it dosn't make a diference weather it's twin or single. Having said that, you'll find that most of the quick or powerfull turbo four or sixes only have a big single turbo where as the big v8s have twin. On a V8, in theory twin should be slightly better as the turbo's are closer to the engine and the exhoust gases are hotter entering the turbos and therefor the turbos would spooll up quicker. The downside of twin is the extra cost, extra wheight, more complex and the combined enertia of the turbos is more. I went with a single turbo as the cost was less, I din't have room for twin, less complex and achieved the same resolts. At the end of the day, you can achieve the same resolts with a single or twin with the only difference being bragging rights of a twin setup. (is it worth the cost?).
As with most things that come with these type of cars, the intercooler is a custom one off job. We went with a water to air intercooler as we couldn't fit a large enough air to air in the engine compartment. Hope that helps.
To answer your question om which is better single or twin is a bit hard to answer without more info. (budget, room, purpose of car etc). I've read that Porshe has done some resarch into the matter and has concluded that if the turbos are appropriately sized, then it dosn't make a diference weather it's twin or single. Having said that, you'll find that most of the quick or powerfull turbo four or sixes only have a big single turbo where as the big v8s have twin. On a V8, in theory twin should be slightly better as the turbo's are closer to the engine and the exhoust gases are hotter entering the turbos and therefor the turbos would spooll up quicker. The downside of twin is the extra cost, extra wheight, more complex and the combined enertia of the turbos is more. I went with a single turbo as the cost was less, I din't have room for twin, less complex and achieved the same resolts. At the end of the day, you can achieve the same resolts with a single or twin with the only difference being bragging rights of a twin setup. (is it worth the cost?).
As with most things that come with these type of cars, the intercooler is a custom one off job. We went with a water to air intercooler as we couldn't fit a large enough air to air in the engine compartment. Hope that helps.
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Definately not trying to be different. Most interested in proven paths! Who did the work in the photo's above? Is that type of set up available in a kit or is it custom? What single Turbo is being used in photos--ie model .
Is there anyone,anywhere doing single or twin kits that are GT40 specific?
I have Porsche experience of both single and twin and I am trying to do some research for a GT40 for someone not computer aware to try and get him going in the right direction ! All help appreciated.
Is there anyone,anywhere doing single or twin kits that are GT40 specific?
I have Porsche experience of both single and twin and I am trying to do some research for a GT40 for someone not computer aware to try and get him going in the right direction ! All help appreciated.
There are some guys guys doing turo kits for the Ford GT but no one does kits for the GT40. It would be hard to make a kit for the 40 as they are all slightly different in many ways are the interest in turbos from the more mature owners is limited.
The work in the pictures is mostly done by me and it's all custome one off. The turbo used is a Garrett GT51R rated at 1,000hp and it's been twiked up a bit.
The work in the pictures is mostly done by me and it's all custome one off. The turbo used is a Garrett GT51R rated at 1,000hp and it's been twiked up a bit.
That is fundamental advantage of going twin. Two turbos can equal the same amount of air to give equal end HP but with much quicker spool up that in my experience can virtually eliminate lag.
While a big single may produce huge number that might be ok on a drag strip it does nothing for general driveability. I am always bothered by the idea of massive HP that is effectively unusable - so what point does it achieve?
Anyone with experience of twins?
Red9, your missing the point. The most important thing is to choose a turbo or turbos which are suited for the application. What I mean by this, lets say your chasing 600hp, you could choose one Gt35/40 which is rated at 650hp or run two T28's which are rated at approx 300-350hp. Both of these would work fine. One thing to remember is when you run twin, you only have half the energy to run each turbo and they need to be sized appropriately. If you get the sizing wrong on a twin application and go too big, the lag would be way worse than a big single. In an ideal world, I would run twin on a V engine and single on an inline engine, and I would keep the turbos as close as possible to the exhoust manifold. They all have their advantages.
Attached is the dyno sheet of my GT40. The boost control is taken care of by the Haltech ecu. I also tried a friends Turbosmart E-Boost 2 boost controller and the boost came on much earlier (about 400rpm), and I'll be changing to that soon. We let the car coast on the dyno at about 2,500rpm with no positive boost pressure and then we floor it. With the E-Boost controller, we had 0.5bar at 3,300rpm and full boost at just over 4,000rpm and that is with a motor with stock standard heads, valves, valve springs, totaly untouched heads. We achieved that using Shell V-Power with 5% ethenol. One thing we found is the stock valve springs are at their limit and start to float at boost levels above 20psi.
Attached is the dyno sheet of my GT40. The boost control is taken care of by the Haltech ecu. I also tried a friends Turbosmart E-Boost 2 boost controller and the boost came on much earlier (about 400rpm), and I'll be changing to that soon. We let the car coast on the dyno at about 2,500rpm with no positive boost pressure and then we floor it. With the E-Boost controller, we had 0.5bar at 3,300rpm and full boost at just over 4,000rpm and that is with a motor with stock standard heads, valves, valve springs, totaly untouched heads. We achieved that using Shell V-Power with 5% ethenol. One thing we found is the stock valve springs are at their limit and start to float at boost levels above 20psi.
ditto what Bobski said.
There's actually been a renewed interest in twin turbo configurations with a new twist: differential sizing. In other words, one small turbo spools up early on light/part throttle and the larger turbo spools up when the butterfly is more open and the rpm has come up. Turbo diesels are using this technology and there have been a few gasoline engines employing it as well. It's intriguing and makes some good logical sense - sort of a compromise "best of both worlds" approach.
There's actually been a renewed interest in twin turbo configurations with a new twist: differential sizing. In other words, one small turbo spools up early on light/part throttle and the larger turbo spools up when the butterfly is more open and the rpm has come up. Turbo diesels are using this technology and there have been a few gasoline engines employing it as well. It's intriguing and makes some good logical sense - sort of a compromise "best of both worlds" approach.
Not to sure what point you think I am missing - so I will state it even louder. Smaller turbos boost earlier and faster. Fact. The presumption is that thaey are configured for the purpose at hand. They can be designed to equal the equivelent end HP. So in an ideal world-why would you go single?
The idea of progressive turbos was on production RX7 and is probably overcomplex to have widespread application . With proper engine management system and programming,the right turbos, lag can be nearly eliminated .
The idea of progressive turbos was on production RX7 and is probably overcomplex to have widespread application . With proper engine management system and programming,the right turbos, lag can be nearly eliminated .
So the new mercedes s-class diesel and the new bmw 535d (both using a sequential twin turbo system) are "overly complex to have widespread application" ?
Apparently those manufacturers are seeing some logical value. Perhaps it's limited to diesel application only, and if so then that's not a big help for a Ford V8 gasoline engine in a GT40 obviously...
Big Red, you've missed it again. We all that samller turbos do spool up earlier and faster. Fact. In a twin setup, each turbo gets half the energy to drive it. Fact. The combined enertia mass and weight of twin turbos is more than the equivalent single. Fact. So when you consider all the facts, I wonder how you can conclude a twin setup to be always better than a single setup? On a V type engine the advantage is mentioned above. On an inline engine, the only advantage in going twin is when they're configured to be sequential. In otherwords, by them being a different size, the smaller turbo gets the motor going and the second bigger turbo takes over.
If what you say is true, than each and every single turbo race car would be a twin setup. In reality, majotity of turboed race cars are infact sinle turbo. Just look at the world rally cars. Need I say more?
If what you say is true, than each and every single turbo race car would be a twin setup. In reality, majotity of turboed race cars are infact sinle turbo. Just look at the world rally cars. Need I say more?
There are many issues to consider. The exhaust turbine housing size will directly correlate to the point at which the positive pressure is produced. Case in point, I had a Nissan GTiR Pulsar running a big single Trust Hybrid T78 on a stroked 2.2ltr SR20. Initially it made no boost below 4400rpm. I modified the exhuast turbine to a smaller spec, and had pressure from 3500rpm. Peak boost was limited to 2.4 bar in both scenarios. All wheel drive burnouts are cool - just not at 60km/h.
Talking of diesels, two of the big fast ferries that I engineered on ran triple MTU V16 with twin sequential turbochargers. The first would boost from 900rpm to 1600rpm, the second was designed to spin from 1400rpm all the way to 2150rpm. On a 40 mtr aluminium monohull with three 32ltr V16s, you could really feel when all three MTU's were all pushed onto the second turbo. You should have seen them glow at full boost!
Talking of diesels, two of the big fast ferries that I engineered on ran triple MTU V16 with twin sequential turbochargers. The first would boost from 900rpm to 1600rpm, the second was designed to spin from 1400rpm all the way to 2150rpm. On a 40 mtr aluminium monohull with three 32ltr V16s, you could really feel when all three MTU's were all pushed onto the second turbo. You should have seen them glow at full boost!
I don't have a problem, I just push the gas pedal sooner in a corner. In the racing application I like the big single air/air IMSA turbo vs. the water/water twin turbo setup.
No doubt a small twin setup can make some serious hp too - Red9 is onto something here as well. I had a maserati bi-turbo (3.0ltr injected twin turbo) and holy smokes that thing had some fat mid-range hp. From 2,500 to 4,000rpm it was nuts....could break the rear wheels loose at freeway speeds on dry pavement. It was actually kind of scary to do that in a four seater sedan type car with soft susension.
This fight will go on forever. Entrenched believers on either side are hard to sway. I am on neither side - I have single and twin setups in different cars and I will continue to believe that both setups can deliver pretty similar results if setup correctly.
Bobski is on the money IMO.
Coincidentally my comparable setups are extremely similar to the 600bhp scenarios described by him earlier - 1 X GT35/40 vs 2 X HKS GT SS.
Currently my big single is quite responsive on it's 2.5 litre engine whereas I am chasing response on my twin turbo 2.6.
However, I am confident that both will perform similarly when the twin turbo car is fully sorted.
To be fair the engines are not identical, the 2.5 is a flat 4 (Subaru) and the 2.6 is an in-line 6 (Nissan GT-R) and these have different characteristics all on their own but I felt compelled to join in when Bobski nailed my setups.
Whichever you believe in, go for it.
Tim.
Bobski is on the money IMO.
Coincidentally my comparable setups are extremely similar to the 600bhp scenarios described by him earlier - 1 X GT35/40 vs 2 X HKS GT SS.
Currently my big single is quite responsive on it's 2.5 litre engine whereas I am chasing response on my twin turbo 2.6.
However, I am confident that both will perform similarly when the twin turbo car is fully sorted.
To be fair the engines are not identical, the 2.5 is a flat 4 (Subaru) and the 2.6 is an in-line 6 (Nissan GT-R) and these have different characteristics all on their own but I felt compelled to join in when Bobski nailed my setups.
Whichever you believe in, go for it.
Tim.
