M5 twin turbo

[ciderisgr8]

While looking at the Veyron prang website I decided to look at the link to the M5 twin turbo.Here (http://www.motorauthority.com/news/sedans/currency-motors%e2%80%99-800hp-twin-turbo-m5/) Did anyone else pick up on the fact that its turbos are mounted under the rear bumper ?
It must take a bit of umph to get them upto speed and then to get them to force the air all the way to the engine.
Sounds like a bit of a beast though /Devil5

[bradc]

sounds quite silly to me, heaps of lag, and by the time the exhaust gets down there it will be quite cool as well.

[Wodjno]

and by the time the exhaust gets down there it will be quite cool as well.


Thats good ain't it ???

[ralliart-type-s]

S'pose it keeps the hot air outta the engine bay. lag depends on turbo size and whether sequential or not tho doesnt it??

[Wodjno]

S'pose it keeps the hot air outta the engine bay. lag depends on turbo size and whether sequential or not tho doesnt it??

I would agree with the above.. Also wih 501 GG's already under the bonnet :D

I don't think Lag will be to much of a worry ;)

[bradc]

wodj, thats bad, turbos get their power (or at least 70-80%) from heat

[Wodjno]

wodj, thats bad, turbos get their power (or at least 70-80%) from heat

I thought they got Most there heat from all the Power ??

[bradc]

???

The long exhaust section will let a lot of heat escape, so it won't be very good at all for keeping the energy up nice and high when the air hits the turbine

[d i c k i e s]

damn turbos coming off the exhaust.. thats mean! location, at 800HP could you tell the difference anyway?

[Wodjno]

???

The long exhaust section will let a lot of heat escape, so it won't be very good at all for keeping the energy up nice and high when the air hits the turbine

But also the air is being allowed to cool after it has been superheated by the Turbo's, on it's way back to the front of the car to enter the engine.. I'm Sure 1 cancels out the other :pimp2:

[bradc]

thats what the intercooler does anyway :)

[Wodjno]

thats what the intercooler does anyway :)
Hmmm ! Thanks for that Brad :thinking: I wondered why i installed a 600x300x100 FMIC.. I thought it was a new Heater Rad for the Cabin /rally

OK.. Lets put it like this !!

Every Standard Turbo car that is produced to my knowledge, can be made more powerful by reducing the heat of the air that is entering the cylinders.. The Colder the Better..

1st stop is either a cold air box(which we alreadyhave) or a Larger, more efficient FMIC.. Both of which are for the benefit of cooling or keeping the air as cool as possible.

So with the above Bimmer, the exhaust gases are expelled from the exhaust manifold and make the way down the long exhaust to the rear of the car and to the turbo's. On this journey(as you have already said Brad) the Gases are cooling down, so when they reach Turbo's, this must mean that they are not generating as much heat as they would if they were only 2 or 3 feet away.. So then the Air that is entering the Turbo's will effectively not be as hot as it would normally be when exiting the Turbo's. Then it has it's journey back up the long intake pipe(where it is cooling) and into the FMIC(where it is made even Cooler) then from there into the Intake manifold... :pimp2:

The End result being that the air is bound to be colder than a normal set up.. And Colder air in the cylinders, means more dense air, which means more fuel being added and a bigger bang... :scholar: MORE POWER per PSI /yes

Waits for the barage of abuse :inquisiti

[WildCards]

Cold air is better due to increased density. Higher Density means more oxygen means better combustion means more power, but haven't people had problems with air being too cold from oversized IC's?

Brad, are you saying that hotter air should pass through the turbo system to make it work and be cooled just before entering the engine?

[Wodjno]

Cold air is better due to increased density. Higher Density means more oxygen means better combustion means more power, but haven't people had problems with air being too cold from oversized IC's?

Brad, are you saying that hotter air should pass through the turbo system to make it work and be cooled just before entering the engine?

Err ?? To much Cold air in the engine can never be a bad thing :inquisiti Otherwise Nitrous Oxide wouldn't be of any use(still got 2 Full kits here if anyone is after 1 );)
I can see where Brad is coming form though...

Lets say 2 Cubic Ft of Exaust Gases exit from the Exhaust manifold and into the exhaust and is heading down to the Turbo's !! What Brads saying is, what starts out to be 2 Cubic Ft of Exhaust Gases may by the time it reaches the Turbo's only be 1.8 Cubic Ft of Gas as it has cooled and become more dense ! This means the pressure in the pipe is not as high, thus meaning not as much force is being exerted on the the turbine, so it won't spin as fast and won't create as much PSi for the same amount of exhaust gas, as it would if the Turbo's were only a couple of feet away :speechles

[WildCards]

Err ?? To much Cold air in the engine can never be a bad thing :inquisiti Otherwise Nitrous Oxide wouldn't be of any use(still got 2 Full kits here if anyone is after 1 );)
I can see where Brad is coming form though...

Lets say 2 Cubic Ft of Exaust Gases exit from the Exhaust manifold and into the exhaust and is heading down to the Turbo's !! What Brads saying is, what starts out to be 2 Cubic Ft of Exhaust Gases may by the time it reaches the Turbo's only be 1.8 Cubic Ft of Gas as it has cooled and become more dense ! This means the pressure in the pipe is not as high, thus meaning not as much force is being exerted on the the turbine, so it won't spin as fast and won't create as much PSi for the same amount of exhaust gas, as it would if the Turbo's were only a couple of feet away :speechles

Furry muff, I clearly need to lose more hair until i'm as clever as you :afro:
Wasn't their some talk about one of the NZ members using an IC so big the car stalling due to not managing the large amounts of cold air?

Or have I just made that up?

[Wodjno]

Furry muff, I clearly need to lose more hair until i'm as clever as you :afro:
Wasn't their some talk about one of the NZ members using an IC so big the car stalling due to not managing the large amounts of cold air?

Or have I just made that up?

I'm far from Clever :inquisiti But i think you already know that /pan

Not sure about the NZ thing !! I'm running a 600x300x100 with no issues whatsoever.. :D

[pezza]

I'm far from Clever :inquisiti But i think you already know that /pan

Not sure about the NZ thing !! I'm running a 600x300x100 with no issues whatsoever.. :D


Yes but how does that explain how the rest of your engine bay is so cold? Even after excessive raggin? :thinking:

That M5 must be an absolute animal, if it wasn't already one. Bet the turbos sound great being external and all that :-) Probably sounds like thunderbird two ready for take off... :afro:

[Nick Mann]

I think you have started to argue yourselves back to the right argument! The air cannot be too cold - that will not lose you power. However, the capacity of the system can be too large, which is what creates lag. Two tiny turbos trying to pressurise a massive intercooler is simply not going to be efficient! The volume of those pipes on the M5 is a similar thing - it has to be pressurised before the turbos start force feeding the engine - the bigger the volume, the longer it takes to pressurise, the longer it takes for the power to kick in.

Savvy?

[d i c k i e s]

woooooaaa, gone over my head with this info... keep going.

[WildCards]

Savvy?

Savvy, mon ami.

[Wodjno]

I think you have started to argue yourselves back to the right argument! The air cannot be too cold - that will not lose you power. However, the capacity of the system can be too large, which is what creates lag. Two tiny turbos trying to pressurise a massive intercooler is simply not going to be efficient! The volume of those pipes on the M5 is a similar thing - it has to be pressurised before the turbos start force feeding the engine - the bigger the volume, the longer it takes to pressurise, the longer it takes for the power to kick in.

Savvy?

So !! Are you saying what they done is good ?? Or bad ??

I say it is good.. Obviously they pust have matched the Size of the Turbo's to the Size of the system.. And as already stated, with 501bhp for the NA Engine it ain't exactly lacking power before the Turbs Kick in.. So to me, Lag ain't going be much of an issue.. And having to travel all the way back to the front of the car the air is cooling, which is also good..

So to me it's good all round.. And with 810bhp to boast about, only the seriously retarded can say that it's a bad set up :scholar: thats a 60% power increase :D

[bradc]

.. So then the Air that is entering the Turbo's will effectively not be as hot as it would normally be when exiting the Turbo's. Then it has it's journey back up the long intake pipe(where it is cooling) and into the FMIC(where it is made even Cooler) then from there into the Intake manifold... :pimp2:

The End result being that the air is bound to be colder than a normal set up.. And Colder air in the cylinders, means more dense air, which means more fuel being added and a bigger bang... :scholar: MORE POWER per PSI /yes

Waits for the barage of abuse :inquisiti



NO, because the air that comes out of the engine all hot and excited that goes through the turbo doesn't go back into the engine, it goes out the exhaust. The cold air that goes back into the engine is sucked in by the compressor wheel on the turbo that you want to spool up as quickly as possible, which isn't going to happen if you have semi-warm exhaust gases hitting the turbine 5 hours after you hit the throttle!

[bradc]

Brad, are you saying that hotter air should pass through the turbo system to make it work and be cooled just before entering the engine?


You want the air to go through the turbo exhaust turbine as hot as possible so that it's volume is as big as possible so that it spins the turbine as fast as possible.

The air that gets sucked in by the compressor should be as cold as possible, but thats up to the intercooler to do it's job, and isn't related at all to how hot the turbine is, apart from a small heat soak that will occur due to normal heat transfer (but not very much obviously)

[bradc]

Err ?? To much Cold air in the engine can never be a bad thing :inquisiti Otherwise Nitrous Oxide wouldn't be of any use(still got 2 Full kits here if anyone is after 1 );)
I can see where Brad is coming form though...

Lets say 2 Cubic Ft of Exaust Gases exit from the Exhaust manifold and into the exhaust and is heading down to the Turbo's !! What Brads saying is, what starts out to be 2 Cubic Ft of Exhaust Gases may by the time it reaches the Turbo's only be 1.8 Cubic Ft of Gas as it has cooled and become more dense ! This means the pressure in the pipe is not as high, thus meaning not as much force is being exerted on the the turbine, so it won't spin as fast and won't create as much PSi for the same amount of exhaust gas, as it would if the Turbo's were only a couple of feet away :speechles


EXACTLY!!!! :D :iloveyou:

[bradc]

Furry muff, I clearly need to lose more hair until i'm as clever as you :afro:
Wasn't their some talk about one of the NZ members using an IC so big the car stalling due to not managing the large amounts of cold air?

Or have I just made that up?


BDA had some issues with that, but I think that might have been partially due to the tune his car was in, and it just didn't like the intercooler without being re-tuned. If you have a huge volume in the intercooler + piping then the lag can increase, just like with this BMW where you have a 4 meter long exhaust tube which will increase the time it takes for the turbo to start spinning, then you have another 4 metres of pipe for all of the compressed air to go all the way back up to the engine.

[bradc]

So !! Are you saying what they done is good ?? Or bad ??

I say it is good.. Obviously they pust have matched the Size of the Turbo's to the Size of the system.. And as already stated, with 501bhp for the NA Engine it ain't exactly lacking power before the Turbs Kick in.. So to me, Lag ain't going be much of an issue.. And having to travel all the way back to the front of the car the air is cooling, which is also good..

So to me it's good all round.. And with 810bhp to boast about, only the seriously retarded can say that it's a bad set up :scholar: thats a 60% power increase :D


I maintain it is bad, the air that is going back up to the engine bay is supposed to be cooled by an intercooler which has a huge surface area to cool it with, rather than the small area of piping, the big problem is the time it takes to get all of the air back up to the front of the car. Also the M5 isn't known for it's low end torque so putting the turbo's on it will potentially make it more sucky at the low end.

[Wodjno]

You want the air to go through the turbo exhaust turbine as hot as possible so that it's volume is as big as possible so that it spins the turbine as fast as possible.

The air that gets sucked in by the compressor should be as cold as possible, but thats up to the intercooler to do it's job, and isn't related at all to how hot the turbine is, apart from a small heat soak that will occur due to normal heat transfer (but not very much obviously)

Yes i know the Exhaust gases entering the Turbo exit via the exhaust.. /pan What i am saying is(this is where we don't agree) The air going into the Turbo's is being superheated, not as you suggest not much obviously, only a little heat soak :speechles

I think you will find a considerable difference from the Ambient air temp entering the Tubo's to the charged air exiting /pan

EG.. If Ambient air entring is 20C the air exiting could be anything from 100C to 180C.. An Intercooler at it's best will only have an efficiency of 70%, thus reducing 100C back down to 30C and 180C down to 54C.. so still way above the ambient temp entering..
So with the BMW M5 set up.. Any heat soak that is occuring by travelling back along the 4m length of pipe can only be good.. If it only drops the the exiting air from 100C to 90C, an Intercooler with an efficiency rating of 70% will then be able to reduce the charged air down to a temp of 27C instead of 30C if it hadn't travelled along the 4m long section of pipe.. Meaning the air is now more dense when entering the inlet manifold.. Thus Allowing more fuel to be mixed with the larger volume of oxygen, resulting in more power.. /yes

Hope this makes sense to all.. I've tried to describe it so all can understand :D (Steve) ;)

[bradc]

Yeah, but the charged air exiting the compressor is hot because it has been compressed, and because of the internal temperature in the turbo. While there will be a difference depending on how hot the air is on the turbine side of the turbo, the intercooler will cool it down and cater for that difference.

I still maintain that the car will be laggy and the turbos won't be very responsive.

[ralliart-type-s]

Yeah but, we dont know the dia of the pipework, to go through/under the car it cant be too large, this would affect the volume and speed of the charge( ie pressure). smaller pipe work would be best obviously. Unless he's utilising some kind of hogwarts originated jiggery-pokery it would be almost impossible to retain boost through large pipes over such a distance but it would aid prevention of turbo stall w/out the need for a BOV. Maybee he has no intercooler and uses the long pipes to do the cooling and inc boost pressure?? What size turbos are they?? anyone had a look?

[WildCards]

NO, because the air that comes out of the engine all hot and excited that goes through the turbo doesn't go back into the engine, it goes out the exhaust. The cold air that goes back into the engine is sucked in by the compressor wheel on the turbo that you want to spool up as quickly as possible, which isn't going to happen if you have semi-warm exhaust gases hitting the turbine 5 hours after you hit the throttle!

I didn't know that, I understand know. Thanks

[bradc]

Ralliart, yes he could use a smaller intercooler in conjunction with those longer pipes, but you don't have much surface area on those round smooth pipes compared to the fins on an intercooler, so the cooling effect wouldn't be as pronounced as a shorted tubing setup with a big intercooler

Steve - we need to get a real car for you again soon :)

[psbarham]

can i just add before wodj nips over to NZ to insert a FMC and tdo4 up brads Khyber pass , that the whole car is an advertising 'my dicks bigger than your dick ' ploy , its about the no.s nothing else ,its looks like someones gone
'ooh i have a gimmick that no one else has thought of , we'll put the turbos behind the rear bumper' the whole set up looks a bit of a bodge , look at the welding and design of the tail pipes , the way they've realised the engine won't provide sufficient oil pressure all the way back there so they've put a booster pump of sorts there , the whole car is an afterthought .

[Kenneth]

can i just add before wodj nips over to NZ to insert a FMC and tdo4 up brads Khyber pass , that the whole car is an advertising 'my dicks bigger than your dick ' ploy , its about the no.s nothing else ,its looks like someones gone
'ooh i have a gimmick that no one else has thought of , we'll put the turbos behind the rear bumper' the whole set up looks a bit of a bodge , look at the welding and design of the tail pipes , the way they've realised the engine won't provide sufficient oil pressure all the way back there so they've put a booster pump of sorts there , the whole car is an afterthought .

Agreed.

They have also heat-wrapped everything to try and keep the temps up/down to retain as much efficiency as possible.

Having the exhaust outlet to atmosphere directly bolted to the turbo outlet is cool though, I wonder if the efficiency gains come anywhere near the losses for having the turbos at the back of the car though.

btw, how cold the air is when it hits the compressor wheel is VERY important, the more dense it is the more efficiently the compressor works and the greater the air flow. cooling it at the intercooler is useful as it prevents detonation, but it is the air density that comes from the compressor that PUSHES that air through the system. Doesn't matter how cold the air is in the IC, you still have to have enough air replacing it.

[valmes]

Theories are all good, but here are the real world facts:

Year: 2001 Corvette Z06
Best 1/4 mile ET: 7.549
Best 1/4 mile MPH: 187.89
Custom Vette Doctors 422 cubic inch LS2 stroker with a single rear mounted 106 mm turbo.

... that is also completely street legal.

http://www.thevettedoctors.com/05_paul-m.shtml
http://forums.corvetteforum.com/showthread.php?t=1403429

[Subaru ETA]

i would have thought that there would be a **** load of lag! gas has to teavel to the back of the car, spin the turbo, then go all the way back! bmw's like that are just for tossers anyway so when they go to the country club they can say "o look my turbos are back there..." butin the back of there head they wouldnt have a clue who or what a turbo is! :p

[Wodjno]

can i just add before wodj nips over to NZ to insert a FMC and tdo4 up brads Khyber pass

Theres possibly more chance that you'll wake up 1 day to find a Spoiler up your's :inquisiti