Garret GT3076R - experienced opinions? - Vs 3071?

[Rishi]

I'm interested in getting my head round the 3" elbow vs boost surge vs turbo response.

Think of it like this...

The quicker you can get the gas out, then the quicker you can get it in. Thus engine works faster.

Now if your 2.5" turbo elbow is restricting your gas flow then there is only so much that can be expelled from the Turbo at any given rpm.

If you increase the flow capacity of the turbo elbow then the turbo has less back pressure and is able to expell more gas at the same given rpm.

Because the turbo is expelling more gas at the same given rpm level the turbine must be spinning at a greater rate yet at the same engine speed.

Thus you have just increased the spool and response of the turbo.

Now with this the turbo is going to spool up at a greater rate. Using a the tiny internal wastegate to suggenly hold at a set boost isn't going to be easy. It just can't expell enough gas through the wastegate quick enough to stop it over boosting for a moment.


I'm sure there are some others with different ideas but thats my view on it all.



Rishi

 

[campbellju]

Cheers Rishi.

I need more data but I'm convinced its my 2.5" elbow/exhaust that is giving my smoothish Torque curve from 2200 to 4500 (Shown on the G-tech not RR) but limiting torque in the 3-4K range and rate of boost climb in this area. But it is a nice car to drive on the road or track with its NA like response and will crack 60-100 in under 5s according to the datalogit. My aim has always been to build a low lag car rather than a max hp one but I can feel a little more research on the exhaust side coming on.

 

[bracpan]

Been recomended this

http://www.aet-turbos.co.uk/turbo_services.htm

from AET, they say the VT153-86 ( its a 2971) turbo, said they have had good results and its in between the 2871 and the 3071 ( suppries suppries) anybody used one of these? resonable price to.
Cheers
Phil

 

[Fazz]

Reasonable price???

Firstly its a garrett copy. Which can only be a bad thing imo. But by looks of it is uses the Garrett anyway. Same as HKS.

Secondly £900 + Vat!! so £1,057. Thats a lot more than atp or anywhere etc.
Its more than the group buy on 3071 at Fusion as well...

So more expensive, and not as well used.

That be a no then. Go to Fusion or atp lad.

Been recomended this

http://www.aet-turbos.co.uk/turbo_services.htm

from AET, they say the VT153-86 ( its a 2971) turbo, said they have had good results and its in between the 2871 and the 3071 ( suppries suppries) anybody used one of these? resonable price to.
Cheers
Phil

 

[Fazz]

Cheers Rishi.

I need more data but I'm convinced its my 2.5" elbow/exhaust that is giving my smoothish Torque curve from 2200 to 4500 (Shown on the G-tech not RR) but limiting torque in the 3-4K range and rate of boost climb in this area. But it is a nice car to drive on the road or track with its NA like response and will crack 60-100 in under 5s according to the datalogit. My aim has always been to build a low lag car rather than a max hp one but I can feel a little more research on the exhaust side coming on.

Indeed very interesting.

More data to come from me. I'm getting the 3071 and sticking with standard elbow and downpipe to start, so in theory should have similar results to Jim.

This would prove whether the elbow and downpipe is the restricting factor. Unless anyone else here has a 3071 and standard bits same as Jim???

Give me a few weeks and I'll update.

 

[bracpan]

I was quoted cheeper that it said on the site, but that is ready to fit, bolts strait on.

What do you meen by Garret Copy? Thought it was a Garret?

These are the people that done Lou's turbo's so would imagine they know there stuff. Plus remember the extra cost you will probably have to pay when importing from the States, VAT etc,,,plus what do you do it goes wrong? Its a double edge sword when buying from abroad. I am still not convinsed its the best way, but will keep looking for your posts with great interest.

Cheers

Phil

 

[Fazz]

sorry yes they are mostly all Garrett anyway. Just the internals vary afaik.

And they should all bolt straight on with T25 flange etc.

What price was quoted to you?

I'd still wo with one of the others as they are proven and also fit fine.

 

[Trip]

Exhaust - using a 2.5" elbow will restrict your spool to a point. The Dentist did some dyno testing with differnt exhaust sizes... 3" was ideal for the 400bhp turbo they were using but going to the 3.5" exhaust caused a slower spool. Don't think the turbo was large enough to make use of the higher flow capability at the top end. It was the smaller 3" exhaust that proved the better option in this case as the slight back pressure helped spool the turbo quicker. Just shows that you need to be careful what you chose and that biggest exhaust isn't always best.

I will elaborate on this subject. (Just my opinion, I could be totally wrong though)

If the exhaust gasses can depart from the turbo more quickly and efficiently, the turbo can spin more freely thus generating less lag. For this to be accomplished the turbine outlet/down pipe must be efficient enough not to create back pressure. The faster the exhaust gasses can come out the faster is the spool.

The theory behind having a too large diameter comes into play about temperature. Cold air is more dense (heavy) thus needing more energy to flow. So ideally we want to keep our exhaust gasses as hot as possible. Too large a diameter down pipe can hold more gasses (at any given time) thus allowing more time for the gasses to cool.

Also taking into consideration the pulses Vs velocity of the gasses. The larger the diameter the slower is the pulse. Fast pulses = fast moving gas

It’s basically a compromise and there is no formula to get this right. It’s a simple trial and error situation.


I am looking into making an exhaust system jutting out from the front of the driver’s right wheel. 3” and very short. I will use a muffler just to keep the DB’s at a decent level. I will vent the waste gate separately :twisted:

 

[tro||]

It’s basically a compromise and there is no formula to get this right. It’s a simple trial and error situation.

there are some basic graphs available for exhaust diametre and rough power levels aswell as complicated formula for effects of pipe diametre on temperature/gas velocity.

if you are boring enough to be interested in that sort of stuff there are formulas for just about everything on this planet tbh :lol:

 

[Fusion Ed]

I will elaborate on this subject. (Just my opinion, I could be totally wrong though)

If the exhaust gasses can depart from the turbo more quickly and efficiently, the turbo can spin more freely thus generating less lag. For this to be accomplished the turbine outlet/down pipe must be efficient enough not to create back pressure. The faster the exhaust gasses can come out the faster is the spool.

Spot on. However some back pressure in some instances can be desirable as it can improve midrange torque, however always at the expense of top end power. Its a finely balanced compromise.

The theory behind having a too large diameter comes into play about temperature. Cold air is more dense (heavy) thus needing more energy to flow. So ideally we want to keep our exhaust gasses as hot as possible. Too large a diameter down pipe can hold more gasses (at any given time) thus allowing more time for the gasses to cool.

This is actually the wrong way round. Ignore the weight of the exhaust gasses, in this case that really has no issue. Its the volume the gasses take up at the turbo end they contain alot of thermal energy, and so consume alot of space, so at this point you require the largest pipework, as the gasses cool the volume becomes less and so you can get away with slightly (and i do mean slightly) thinner pipework than the front section. (applies for both turbo and NA cars)

Also taking into consideration the pulses Vs velocity of the gasses. The larger the diameter the slower is the pulse. Fast pulses = fast moving gas.

The pulses are created by the opening of the exhaust valves, not the velocity of the gasses, the velocity of the gasses is related to the volume of gasses and the area in which they are trying to pass.

Just want to add also that our 3071 price (965) include all vat postage etc.

Ed

 

[campbellju]

Thanks Evan/Ed, the mists are clearing. I still would like to do some more research and testing but I'm wondering if a lagged 3" downpipe into my 2.5" section might be the next move. There's the NW RR day in the next weeks and that should give some more definitve results than my G-Tech.

Cheers,
Jim

 

[Trip]

Ed,
Since I am also a Honda franatic and I am a member of the S2ki Cummunity and regularly read the NSX prime forum, I read/research loads of informative (or totally bullshit) stuff about tuning etc..

let me see if i find that info which can better explain what i've just said.

 

[Trip]

Here you go

We've seen quiet a few "experienced" racers tell people that a bigger exhaust is a better exhaust. Hahaha… NOT.
As discussed earlier, exhaust gas is hot. And we'd like to keep it hot throughout the exhaust system. Why? The answer is simple. Cold air is dense air, and dense air is heavy air. We don't want our engine to be pushing a heavy mass of exhaust gas out of the tailpipe. An extremely large exhaust pipe will cause a slow exhaust flow, which will in turn give the gas plenty of time to cool off en route. Overlarge piping will also allow our exhaust pulses to achieve a higher level of entropy, which will take all of our header tuning and throw it out the window, as pulses will not have the same tendency to line up as they would in a smaller pipe. Coating the entire exhaust system with an insulative material, such as header wrap or a ceramic thermal barrier coating reduces this effect somewhat, but unless you have lots of cash burning a hole in your pocket, is probably not worth the expense on a street driven car.
Unfortunately, we know of no accurate way to calculate optimal exhaust pipe diameter. This is mainly due to the random nature of an exhaust system -- things like bends or kinks in the piping, temperature fluctuations, differences in muffler design, and the lot, make selecting a pipe diameter little more than a guessing game. For engines making 250 to 350 horsepower, the generally accepted pipe diameter is 3 to 3 ½ inches. Over that amount, you'd be best off going to 4 inches. If you have an engine making over 400 to 500 horsepower, you'd better be happy capping off the fun with a 4 inch exhaust. Ah, the drawbacks of horsepower. The best alternative here would probably be to just run open
exhaust!

 

[Trip]

http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm

 

[bracpan]

Getting a few prices for the 3071, most UK prices are around £1000 including VAT.
Will be interested to see what the final price when odering from the States come to.
Cheers
Phil

 

[Fazz]

New 3071R - WG .
New Uprated Actuator
Oil Resistor
Actuator mounting bracket
Courier to Your country

£750-£800 tops.

www.atpturbo.com

 

[campbellju]

Comments for what its worth ;-)

The turbo's Dooie and I use are from turbo Dynamics, we're both very happy.

Phil, I've seen that company you posted on a Gtir forum before (can't remember which one) and IIRC the opinons were positive. On ATP, I might have heard mixed views over quality but it could just have been an isolated case but it might be worth digging around the internet to see if it was or I've got my wires crossed.

On the where do the bits come from? Well when I got my old T28 re-built by Garret in Skemersdale, there was a delay in getting parts from the states!?! Obviously being a global company they get parts manufactured all over but will distribute themselves. Like my own company and many others they may do parts/product exchange with partners or even competitors to reduce supply cost whilst maintaining a broad product range. So the difference between the parts in an ATP/Turbonetcis/Turbo dynamics/anyone else will be minimal but the difference in assembly, quality assurance and service could be larger.

If anyone wants to spend an extra £300 on something they know will work well, given the criticality of the turbo in the way our engines perform I struggle to give a logical arguement. Its a bit like Wilwood vs AP or HKS vs Mallory, you pays your money, you takes your choice.

Fazz, please double check other people's experiences, I might have got it completely wrong?

 

[bracpan]

I tend to agree if it gets under £200 difference then I would probaly go for a UK company. At least I can go and talk to them face to face if there are any problems. But i am still interested what the final price will be from the states including taxes, customs, and any additional pipework, modifications etc.
Cheers
phil

 

[Fazz]

I'll post up as soon as my baby arrives... Hope fitting shouldn't be too bad. But if you have a close supplier it may be worth it for the customer service and after sales option if there is any problems.

I went with the states as we get Raped in Ireland for everyhting. Better off sourcing it abroad is my opinion...

 

[bracpan]

Great, keep us informed.
Cheers
Phil