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

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STATUS Grand Master

STATUS

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Looks like a great upgrade for those who do only the gymkhana and deca days (low and low to mid rpm), rolls off too much up top for my liking (interesting to know the exhaust pressure above 5000?) but boy it would be quite the traffic light hero :) im sure you will sell a truck load. Congrats on another niche segment turbo.

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SoFreshSoClean Proficient

SoFreshSoClean

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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...

If time taken to rev wasnt a factor, then I am speaking the truth. Gear has no relevance to the power produced by the engine . On the street driving is a different story. That's what he's saying...

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

I'm guessing you have one? :)

Harey Veteran

Harey

Posted
Posted
Looks like a great upgrade for those who do only the gymkhana and deca days (low and low to mid rpm), rolls off too much up top for my liking (interesting to know the exhaust pressure above 5000?) but boy it would be quite the traffic light hero :) im sure you will sell a truck load. Congrats on another niche segment turbo.

You mean low to mid speed (say below 110km/h) not low to mid rpm. Same as a standard turbo, it will make power to the limiter in 1st gear almost to the top of second.

I agree on the congrats for the niche segment turbo.

STATUS Grand Master

STATUS

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You mean low to mid speed (say below 110km/h) not low to mid rpm. Same as a standard turbo, it will make power to the limiter in 1st gear almost to the top of second.

I agree on the congrats for the niche segment turbo.

No a customer of mine drove it and said above 5000 it felt flat, which for a turbo that comes in as quick as this does is to be expected.

Harey Veteran

Harey

Posted
Posted
If time taken to rev wasnt a factor, then I am speaking the truth. Gear has no relevance to the power produced by the engine . On the street driving is a different story. That's what he's saying...

I'm guessing you have one? :)

I am talking about the real world.

Not sure who said the second quote, I dont remember saying that.

SimonR32 Grand Master

SimonR32

Posted
Posted (edited)
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?

A car in 4th gear at 6000rpm making 18psi going downhill will be under a lot less load than a car going up a hill at 6000rpm making 18psi... BUT they will both be using the same amount of air from the turbo!!!

The same car in 1st gear at 6000rpm making 18psi going up and down the hill will also be using the same amount of air as well!

Same amount of air is same amount of power!!!

You are getting confused with load causing a turbo to spool up... Of course a turbo will spool up faster in longer gears due to additional load on the engine but once a boost limit is achieved then the load on the engine does not affect the amount of air the turbo flows... This is governed by the type of boost control used.

Thus yes, turbos are laggier in lower gears but if they are falling over top end they do it in all gears (assuming they are not complete dogs of turbos that don't hit the boost control in early gears)!

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...

Read what I wrote again!

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.

Just because you can’t feel the turbo falling over after 5500rpm in 1st and 2nd doesn’t mean it isn’t... It just means that because the acceleration in those gears is faster and your “seat of pants” dyno can’t tell that it is dropping off!

Edited by Cerbera
juggernaut1 Proficient

juggernaut1

Posted
Posted
A car in 4th gear at 6000rpm making 18psi going downhill will be under a lot less load than a car going up a hill at 6000rpm making 18psi... BUT they will both be using the same amount of air from the turbo!!!

The same car in 1st gear at 6000rpm making 18psi going up and down the hill will also be using the same amount of air as well!

Same amount of air is same amount of power!!!

A car in 4th at 6000rpm going downhill, depending on the decline, is likely to be producing vacuum not boost....or have I missed something?

SimonR32 Grand Master

SimonR32

Posted
Posted
A car in 4th at 6000rpm going downhill, depending on the decline, is likely to be producing vacuum not boost....or have I missed something?

Your screaming down the hill on the back straight of Barbs in 4th gear at 6000rpm on gate... Vacuum?!?

joeyjoejoejuniorshabadoo Grand Master

joeyjoejoejuniorshabadoo

Posted
Posted
he means at WOT

great turbo for gymkhana stuff, you could use 2nd for the whole run instead of having to grab 1st to get on boost etc... no good for track work as the heat would be immense unless you short shifted it

I do agree there Nick... For a trackday this turbo would shit you to tears... But for DECA it would be awesome!

Lithium Grand Master

Lithium

Posted
Posted

Very impressive spool for the power it can make, thats awesome - would be interested in knowing the specs of it. I wouldn't put one on an RB25 unless I was aiming for a fair bit less power though, for power to be falling over like that it much be getting quite hot under the collar.

Sounds like something which could be an aweful lot of fun on an RB20!

juggernaut1 Proficient

juggernaut1

Posted
Posted (edited)
Your screaming down the hill on the back straight of Barbs in 4th gear at 6000rpm on gate... Vacuum?!?

When you said 6000rpm I assumed you meant steady state. :3some:

Edited by juggernaut1
Sheriff Wan Proficient

Sheriff Wan

Posted
Posted

Interesting, this does seem to be more of a 2530 replacement though as peak power is higher...

I have a 2530 on RB25 making full boost (15psi) by 2750 and it drops to 13psi by 6,000 and makes an overall 230rwkw.

For a street setup, I got the 2530, and I love it. This turbo seems to be better bottom end, but if it starts to run out of puff by ~4,600 I can't see the benefit. I could just wind the 2530 up some more and let it run off in the same fashion and only sacrifice 250 rpm from an already stupidly low response...

Food for thought.

joeyjoejoejuniorshabadoo Grand Master

joeyjoejoejuniorshabadoo

Posted
Posted

for drift you really wan the maximum powerband....

it'd be nice and easy to get things going in 2nd, but trying to manji a straight in 3rd might be a problem with the power dropping off so severely

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