Atr43ss-2 Prototype Initial Tune 250rwkws 18psi<2500rpm, Stupidly Responsive

[zebra]

Thats fine, go out and buy a GT3076. This turbo is designed for street response. Yeah 18psi at 2500rpm in 4th gear but in say 1st gear your talking about ~4500rpm. If you are trying to use a turbo on the street legally then an extra 50-60hp at the top of 4th gear isnt an issue.

It is great to have different turbo options for different people.

it doesn't matter what gear it is in. it will still nose over after 5500rpm...so it is really only giving a 2500-3000rpm power band at best.

[Harey]

it doesn't matter what gear it is in. it will still nose over after 5500rpm...so it is really only giving a 2500-3000rpm power band at best.

That is incorrect, it does matter what gear you are in. How much air a turbo provides varies with load ie. varies with gear ratio (as diff ratio is constant). Different gears will show different characteristics. A very simple example is how response varies depending what gear you are in. A rough estimate is a difference of 1500-2000rpm between 1st and 4th gears. So if this turbo makes full boost at 2500rpm in 4th gear, its making full boost at 4000-4500rpm in 1st gear.

The amount of air an engine flows varies with load (ie gear). An engine running flat out in 4th gear will be flowing more air than an engine flat out in 1st gear. Therefore a turbo can work well with the amount of air flowing in 4th gear but barely be doing anything in 1st gear. The opposite is also true, a turbo can work well in 1st and 2nd gear but be restrictive in 4th gear.

This is one of the greatest misconceptions about turbocharged vehicles. The key is to get the best compromise for what you want from the car.

Trust me this turbo did not nose over after 5500rpm in 2nd gear

Edited May 10, 2010 by Harey

[Adriano]

Im sorry, i agree with zebra, the engine will only make more torque in higher gears, so the only reason it wouldnt nose over at 5500 in second is because it would be making less torque before that. The other thing is that a drop off in torque is far less noticeable in lower gears.

[SimonR32]

That is incorrect, it does matter what gear you are in. How much air a turbo provides varies with load ie. varies with gear ratio (as diff ratio is constant). Different gears will show different characteristics. A very simple example is how response varies depending what gear you are in. A rough estimate is a difference of 1500-2000rpm between 1st and 4th gears. So if this turbo makes full boost at 2500rpm in 4th gear, its making full boost at 4000-4500rpm in 1st gear.

The amount of air an engine flows varies with load (ie gear). An engine running flat out in 4th gear will be flowing more air than an engine flat out in 1st gear. Therefore a turbo can work well with the amount of air flowing in 4th gear but barely be doing anything in 1st gear. The opposite is also true, a turbo can work well in 1st and 2nd gear but be restrictive in 4th gear.

This is one of the greatest misconceptions about turbocharged vehicles. The key is to get the best compromise for what you want from the car.

Trust me this turbo did not nose over after 5500rpm in 2nd gear

sorry but you are just as wrong as he is...

a turbo flows as much air as needed to build up a set pressure caused by the restriction of the engine (as set by a actuator/wastegate and/or boost controller), it has nothing to do with the load on the engine! thus once the turbo reaches its set boost (and stays there) the power it makes in any gear should be fairly similar.

a engine flat out in 4th gear will flow very similar amounts of air into to a engine as one flat out in first gear (assuming same boost level)

if a turbo falls over in 4th gear at 5300rpm when its running 18psi, then it will also fall over in 2nd gear at 5300 when its running 18psi... just because you can not feel it doesn't mean it isnt happening

[Granthem]

this is based on my car which is normal GTST manual

4.11 diff gears (i assume stock?) with active lsd (stock)

RPM = (SPEED / 28) * 1000

Hmm working on that my car runs out of revs at 6250rpm and makes 340rwhp there. Either the dyno speedo is out, or I have some different diff gears. Power fc def says it hits 7200rpm on limiter

[GTScotT]

While testing the waters with various cars, I ended up reading abit on the supra forums. One thing I picked up from there, being a HIGH HP based forum, is a good method of turbo selection.

The rear housing was selected to determine powerband, a larger housing obviously shifting the powerband higher.

Remember here, if we get a .64 rear housing from a 2860rs for example, and compare it to a .63 rear housing off a 3076r.. which housing is bigger?

We cant always compare housing sizes the same across all turbos.. just because a .63 is too small for one turbo, doesnt make it too small for the next. the HKS GTRS uses a .64 rear housing, its the last turbo ive seen choke on an RB25.

Im pretty sure once Stao works out where the restriction is, he will work on a solution. that waste gate limiter was next to genius IMO.

[hypergear]

Discussion time:

Sam recommended this type of actuator as a solution to boost drop problem:

Boost pressure goes into bottom nipple that forces the diaphragm Up.

The Boost pressure goes into the top nipple to force the diaphragm down.

Manifold pressure escapes by forcing the diaphragm down.

Make this work, you need two boost controllers to bleed certain amount of air in/out to re-enforce pressure on desired side of the diaphragm. Goal is to overcome manifold pressure and stabilize boost pressure.

By my calculation this won't work for this scenario, as exhaust manifold pressure is clearly higher then inlet manifold pressure.

Please let me hear your opinions wither I should invest in this simple setup or should I make a external gate internal which I know for fact that definitely works.

[SoFreshSoClean]

sorry but you are just as wrong as he is...

a turbo flows as much air as needed to build up a set pressure caused by the restriction of the engine (as set by a actuator/wastegate and/or boost controller), it has nothing to do with the load on the engine! thus once the turbo reaches its set boost (and stays there) the power it makes in any gear should be fairly similar.

a engine flat out in 4th gear will flow very similar amounts of air into to a engine as one flat out in first gear (assuming same boost level)

if a turbo falls over in 4th gear at 5300rpm when its running 18psi, then it will also fall over in 2nd gear at 5300 when its running 18psi... just because you can not feel it doesn't mean it isnt happening

You're right, however what really makes a difference is drivability, and the time it takes to rev out each gear compared with the time it takes for the compressor to spool. Sure, an engine with a large compressor may make 300rwkw, but I'm guessing the powerband on an RB25 is realistically only about 1000rpm in first gear, 2000 in second, making it utterly useless at street legal speeds (I'm speaking from experience here). I once tried to get in front of a manual V6 VS ute on a freeway onramp and failed hard

Some may argue that you can rev and dump.. they might also find themselves hoon lawed and without a license

As a side note, I took my friend for a ride in my old standard turboed R33.. he was blown away by the speed of it in 1st and 2nd gear compared to his lag monster big power car!

[Ruffels]

You're right, however what really makes a difference is drivability, and the time it takes to rev out each gear compared with the time it takes for the compressor to spool. Sure, an engine with a large compressor may make 300rwkw, but I'm guessing the powerband on an RB25 is realistically only about 1000rpm in first gear, 2000 in second, making it utterly useless at street legal speeds (I'm speaking from experience here). I once tried to get in front of a manual V6 VS ute on a freeway onramp and failed hard

Some may argue that you can rev and dump.. they might also find themselves hoon lawed and without a license

As a side note, I took my friend for a ride in my old standard turboed R33.. he was blown away by the speed of it in 1st and 2nd gear compared to his lag monster big power car!

TOTALLY AGREE .... my car is a street car... ive never used it for anything more then a street car, and probably wont ever use i for anything more

but i want a useable power range.... not licence loosing power range....

im finding i dont get my huge turbo kick until im breaking the speed limit ... although i do enjoy the huge shove in the seat

[SimonR32]

You're right, however what really makes a difference is drivability, and the time it takes to rev out each gear compared with the time it takes for the compressor to spool. Sure, an engine with a large compressor may make 300rwkw, but I'm guessing the powerband on an RB25 is realistically only about 1000rpm in first gear, 2000 in second, making it utterly useless at street legal speeds (I'm speaking from experience here). I once tried to get in front of a manual V6 VS ute on a freeway onramp and failed hard

Some may argue that you can rev and dump.. they might also find themselves hoon lawed and without a license

As a side note, I took my friend for a ride in my old standard turboed R33.. he was blown away by the speed of it in 1st and 2nd gear compared to his lag monster big power car!

we are on the same page, i was just trying to point out his flawed logic

myself personally, i dont mind a bit more lag to get a bit more power

if you want a bullsh1t fast car, get a GTR with a t04z

[SoFreshSoClean]

we are on the same page, i was just trying to point out his flawed logic

myself personally, i dont mind a bit more lag to get a bit more power

if you want a bullsh1t fast car, get a GTR with a t04z

I didnt really like my KKR480, so I'm getting a GT-RS put on on Wednesday.. should provide a pretty healthy top end kick with minimal lag!

Edit: Sorry for hijacking the thread, looks like a pretty sweet turbo

Edited May 10, 2010 by SoFreshSoClean

[Cartman]

Discussion time:

Sam recommended this type of actuator as a solution to boost drop problem:

Boost pressure goes into bottom nipple that forces the diaphragm Up.

The Boost pressure goes into the top nipple to force the diaphragm down.

Manifold pressure escapes by forcing the diaphragm down.

Make this work, you need two boost controllers to bleed certain amount of air in/out to re-enforce pressure on desired side of the diaphragm. Goal is to overcome manifold pressure and stabilize boost pressure.

By my calculation this won't work for this scenario, as exhaust manifold pressure is clearly higher then inlet manifold pressure.

Please let me hear your opinions wither I should invest in this simple setup or should I make a external gate internal which I know for fact that definitely works.

I know you love the zero lag factor with this turbo however if it was me i'd be looking at stepping up the exhaust housing size a fraction.. with the boost dropping off as badly as it is the amount of extra heat generated could cause alot more problems further down the road, the other thing that would make me lean towards a bigger exhaust housing is the massive drop in power up top, even tho you've got boost dropping off i still dont think getting it to hold boost is goin to drop it from dropping power considering how far out of its efficency range it would be considering the problems your having with the boost drop.

oh and honestly.. i know most of us say we dont give a shit about fuel economy.. 18psi before 2500rpm is unreal,, but think of the highway cruising speeds.. that poor little turbo is goin to be ringing its tits off at 100kph as you cruise down the road and definately not helping fuel consumption, i find it annoying enough with the stock turbo on my temporary rb25.

anyway thats my extremely tired 2cents at 6am in the morning.

[Harey]

sorry but you are just as wrong as he is...

a turbo flows as much air as needed to build up a set pressure caused by the restriction of the engine (as set by a actuator/wastegate and/or boost controller), it has nothing to do with the load on the engine! thus once the turbo reaches its set boost (and stays there) the power it makes in any gear should be fairly similar.

a engine flat out in 4th gear will flow very similar amounts of air into to a engine as one flat out in first gear (assuming same boost level)

if a turbo falls over in 4th gear at 5300rpm when its running 18psi, then it will also fall over in 2nd gear at 5300 when its running 18psi... just because you can not feel it doesn't mean it isnt happening

So turbos are not affected by load... Turbos love load, anyone will tell you that. Thats why they love to climb hills etc. There is more load in higher gears. Simple.

You say I am wrong and then you say the amount of air is 'similar' in all gears. So you agree its not the same, so the only thing we are disagreeing with is how much by.

Why then does a GT35 hardly make boost in 1st gear, make it earlier in second gear and even more useable rpm in 3rd and 4th?

Edited May 10, 2010 by Harey

[Harey]

You're right, however what really makes a difference is drivability, and the time it takes to rev out each gear compared with the time it takes for the compressor to spool. Sure, an engine with a large compressor may make 300rwkw, but I'm guessing the powerband on an RB25 is realistically only about 1000rpm in first gear, 2000 in second, making it utterly useless at street legal speeds (I'm speaking from experience here). I once tried to get in front of a manual V6 VS ute on a freeway onramp and failed hard

Some may argue that you can rev and dump.. they might also find themselves hoon lawed and without a license

As a side note, I took my friend for a ride in my old standard turboed R33.. he was blown away by the speed of it in 1st and 2nd gear compared to his lag monster big power car!

You agree with cerbera and then you say "the powerband on an RB25 is realistically only about 1000rpm in first gear, 2000 in second, making it utterly useless at street legal speeds (I'm speaking from experience here)."

If you agree with cerbera you should have the same amount of useable rpm in 1st and 2nd gears...

Edited May 10, 2010 by Harey

[zebra]

So turbos are not affected by load... Turbos love load, anyone will tell you that. Thats why they love to climb hills etc. There is more load in higher gears. Simple.

You say I am wrong and then you say the amount of air is 'similar' in all gears. So you agree its not the same, so the only thing we are disagreeing with is how much by.

Why then does a GT35 hardly make boost in 1st gear, make it earlier in second gear and even more useable rpm in 3rd and 4th?

That is more to do with that fact that 1st and 2nd gear are way to short in a skyline, so you run out of revs before the turbo has a chance to wind up,

so while this turbo may give instant wheel spin in 1st and 2nd, try winding it out to overtake, these engines need to rev, if you want bulk mid range than buy a big block v8. Having to upshift at 5500rpm on an engine that redlines at 6900 because there is no power up there would annoy the shit out of me.

I also don understand why the boost drops off so badly, my 10year old MTQ rb25 high flow held 16+psi all the way to 7500 with a standard actuator and a manual bleed valve. and made 16psi at 2600rpm.

[Granthem]

I didnt really like my KKR480, so I'm getting a GT-RS put on on Wednesday.. should provide a pretty healthy top end kick with minimal lag!

You will love it! Excellent turbo for street use. It doesnt really run out of legs either.

[juggernaut1]

So turbos are not affected by load... Turbos love load, anyone will tell you that. Thats why they love to climb hills etc. There is more load in higher gears. Simple.

You say I am wrong and then you say the amount of air is 'similar' in all gears. So you agree its not the same, so the only thing we are disagreeing with is how much by.

Why then does a GT35 hardly make boost in 1st gear, make it earlier in second gear and even more useable rpm in 3rd and 4th?

Agreed turbo's like to be loaded because of there inherent lag. A big turbo in 1st gear will not be able to keep up with the flow requirements of the engine. Once a taller gear is selected the engine revs slower and the big huffer is in its element because the compressor has a chance to come up to boost earlier in the rev range. This is why ramp rates of dynos can skew hp figures.

As an extreme example listen to some of those 1000hp youtube dyno's.....they rev the engine to what sounds like around 5000rpm and you can hear the big turbo coming up to speed, and then once up to speed (or loaded) they then do the dyno run.

Edited May 10, 2010 by juggernaut1

[hypergear]

I know you love the zero lag factor with this turbo however if it was me i'd be looking at stepping up the exhaust housing size a fraction.. with the boost dropping off as badly as it is the amount of extra heat generated could cause alot more problems further down the road, the other thing that would make me lean towards a bigger exhaust housing is the massive drop in power up top, even tho you've got boost dropping off i still dont think getting it to hold boost is goin to drop it from dropping power considering how far out of its efficency range it would be considering the problems your having with the boost drop.

oh and honestly.. i know most of us say we dont give a shit about fuel economy.. 18psi before 2500rpm is unreal,, but think of the highway cruising speeds.. that poor little turbo is goin to be ringing its tits off at 100kph as you cruise down the road and definately not helping fuel consumption, i find it annoying enough with the stock turbo on my temporary rb25.

anyway thats my extremely tired 2cents at 6am in the morning.

Well its obviouse that you can hold boost and power better uptop with larger housing and wheel. But on the same time you are shifting power band towards higher RPMs, which is defeating the purpose of building this turbo.

I'm not really on this track, I'm thinking more of bleeding out the excess pressure when overload. which should help to keep the power band steady up top.

[juggernaut1]

Looks like the hypergear turbo is a great street turbo.....unfortunately the turbo (any turbo) can't be all things to everyone.

Edited May 10, 2010 by juggernaut1

[Harey]

That is more to do with that fact that 1st and 2nd gear are way to short in a skyline, so you run out of revs before the turbo has a chance to wind up,

so while this turbo may give instant wheel spin in 1st and 2nd, try winding it out to overtake, these engines need to rev, if you want bulk mid range than buy a big block v8. Having to upshift at 5500rpm on an engine that redlines at 6900 because there is no power up there would annoy the shit out of me.

I also don understand why the boost drops off so badly, my 10year old MTQ rb25 high flow held 16+psi all the way to 7500 with a standard actuator and a manual bleed valve. and made 16psi at 2600rpm.

So you agree the gear (and in effect the load) does make a difference to whether the turbo can spool up. What does a turbo use to spool up: airflow and heat. Therefore there is a different amount of airflow and heat in different gears.

Therefore the amount of heat and airflow at 5500rpm in 4th gear could be closer to 6500rpm in 2nd gear. Therefore why it pulls hard to redline. Similarly it could be 6000rpm in 3rd gear. If you cant overtake with power maxing at 6000rpm in 3rd gear with 250rwkw you prob shouldnt be overtaking.

Nowhere did I say this was the perfect turbo.

I dont understand why the boost drops off so much either and it will be really interesting to see when Stao sorts that out.

The standard turbo drops off over 5500rpm in 4th gear and it doesnt fall over after 5500rpm in 1st or 2nd gear does it.

Edited May 10, 2010 by Harey