GT2871R

GT2876R



Hi guys, At the stage now where I need to finalise my turbo selection as the engine I have for my project will have a freshen up and specced to turbo.
I am not wanting massive power i'd happily settle for a potent responsive setup over big power & top End (hence my 3.6 diff ratios) round about the 400bhp mark.
I've narrowed my selection down to the roller bearing gt series, theyre a lottle expensive but worth it for the added responsiveness they give...which is what i'm after.

It's all going into a Mk1 Fiesta with 4x4 cossie running gear etc... so a decent useable 400bhp would be more than enough without breaking the bank.

The Engine I currently have has 2x BD10 cams in it....ported head (mainly inlet side..exhaust just tickled).
dependant on turbo selection I may ditch the bd10s or just the exhaust cam if it would aid driveability........

So out of the maps @ top of page which one is best suited to a 2 litre cossy of my rough spec?

Cheers
Dan

Info taken from ATP turbo (USA)...http://www.atpturbo.com/Merchant2/me...egory_Code=GRT

 

had them explained to me a few times but I keep forgetting

I know the line of the left of the compressor map is the surge line but thats all i can think of just now

 

You are probably more interested in teh compressor than the turbine, in which case, read my guide here and it may well put you on the right road.

http://www.fastfordmag.co.uk/page/fa.../Tech%20Guides

 

Yeah I am interested in getting the right spec of turbo for my needs, I've seen too many badly specced performance cars not make good power or not be driveable to not be bothered about it.

Ok I've ready your article very well explained! My next question is how much airflow is required on a YB to produce 400-420bhp?

Cheers
Dan

 

Hi,

Divid power request by 10 :
Approx : 40 / 42 lb/mn.

Regards

Claude

 

Right then....been looking at various different turbo compressor maps but want to run this by people who know before looking at pricing a unit up.

If I am correct this turbo (map below) can deliver the 40LB of air I'd need for 400bhp and would still be within its design capabilities, no surge, no choke etc...



Can anyone confirm this turbo would suit my needs? as far as I can see its bang on for what I want.

Many thanks for the link to the article Stu! read a few others since original post and yours sums it all up nicely...

Cheers
Dan

 

Hi,

If i understand STU lesson very well, no, this turbo is not for your requirement, because efficiancy island is out our 400 bhp.
This turbo is good for 300 / 350 bhp only ( 30 / 35 lb/mn. air flow)

For 400 bhp, it is better to use your first map of GT254OR 76 mm. 48 trim, 0,76 A/R. With this, for 400 bhp, you run with 1,8 bar of TC pressure, you are in good position on Efficiancy Island, and you are just on dotted line.

Regards.

Claude

 

here is a link: http://www.turbobygarrett.com/turbob...o_tech103.html

 

Hmm thgats what I thought, I thought maybe I could sacrifice a bit of efficiency top end for lower down poke but if its a unsuited turbo i'll end up hating it anyhow.

So 1.8 bar of boost equates to 2.8 on the map as you already have 1 bar atmospheric am I right? which as you say puts me on the dotted line on the gt2876r map.

I'll get this confirmed and then start to source one

Dan

 

Agree with most of what claude has said, on the maps shown it would be better if the turbo rpm was shown, you know approx how much air the engine must consume 1 pound of air = approx 10bhp, so 400 bhp devided by 10 =40ppm
look at the comp map for the required airflow, and best or at least still good efficiency part of the island on comp map, and the pressure ratio checked against boost pressure, then at the speed the turbo is running at to create the required airflow,
Regards Dave R.

 

ok I get the air comsumption but how has the 1.8bar come about? How do you know what boost is required on a YB?

Thanks for answering my questions fellas much appreciated and i've learnt a lot!

Dan

 

I disagree totally I would say that if 400bhp is the max you are going to want then you go for a turbo that just about is on the map at 400bhp, if you go for one that does it comfortabley it means its laggy as to do 400bhp in a middle island means you need a 600bhp turbo

 

That was my thoughts chip, I want 400bhp and not interested in much else efficiency wise...I want the car to be more about acceleration and not really bothered if the turbo becomes less efficient at high RPM as long as its not going to choke.

My main question still is what pressure ratio am I looking at to get 400bhp? I know I need 40lb/min flow but how do I work out what pressure ratio this is @?

Cheers
Dan

 

You can try to calculate it like described here.
http://www.turbobygarrett.com/turbob.../turbo_tech103 .html