turbo trim

im thinking of a new turbo for the sprint car and it needs to spool fast . what hot and cold side trim combination would offer fast spool but hold boost through the whole rev band. money is a bit tight so these fancy dbb units are out of the question.

ill probably end up going for something cheap and ebayish . i just want to nkow what kind of trim will give me boost early. my gt4088 dosn't boost until 4k , ideall id like to shave 1000rpm off that. it only has to make and hold 9psi.

thanks

Na-t?

Surely hot side a/r is the more important consideration then?

yes na-t and what hotside trim would be good for me? im not the best on turbo sizing

anybody ?

T4 manifold flange? Which cams do you have fitted and do you still have the dizzy? What is the intake pipe size (3in/4in) and exhaust size and flange style (vband or 4 bolt)?

DBB is going to be fairly pointless if you're looking for a smaller faster spooling turbo that the 4088, so that some money saved (and the hassle of adding water cooling).

If the boost level is that low you could get away with a relatively small turbo and not suffer from it getting too choked up at higher rpm's, have you look at something along the lines of a GT35r? A low exducer AR would help spool, but it's getting into diminishing returns with small turbos, considering the boost level again shouldn't present a boost drop at higher rpm's. 0.82 should give great spool.

Do you have a specific budget in mind for the turbo? I.e. £200-300 or are we talking £700-1000?

Had a more detailed look into the cheaper alternatives, it's not something I'd recommend for a road car, but as your circumstances are a little different and you're after a budget option, how about the XS power T70? There only appears to be 2 options for a non-divided hotside trim: 0.68 and 1.0. I think you could get away with a 0.68 and not suffer it choking too much if you have stock NA cams. It should be as close to meeting your criteria (low cost & full boost at 3k rpm under full load), but it won't make the sort of power the 4088 did at higher rpm.

thanks , yest its still stock cams . why would the smaller turbo not make as much power at the higher rpm , i thaught 10psi is 10 psi regardless of the turbo thats making it.

i thaught the 4088 was over kill. i can understand it making more power at higher rpm on a big single converted car running 20+ psi but i would have thaught a small turbo that can make 10 psi up to the redline shouldnt cost power.

not questioning you , id just like more detals as to why this would be for my personal knowlage base

or other option? would bigger cams help my 4088 spool faster?

scratch that, too expensive. stick to turbo plan

Hotside a/r, general rule is the lower the number (to a point) better the spool, i.e. a .65 will spool better than a 1.05, but it strangles more at the top end. As youre only running .6bar or so I think thats the way forward

Also 10psi is 10psi but a larger compressor will move a larger volume of air for that given pressure

thanks , yest its still stock cams . why would the smaller turbo not make as much power at the higher rpm , i thaught 10psi is 10 psi regardless of the turbo thats making it.

You need to think of the volume of air being shoved into the engine and not just the pressure its at.

ah i see , so where does the cold side housing come to play in all this in regards to volume capabilities ?

The bigger the compressor the more air you can shift.

This is a good read

http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech102.html

thats exelent thanks .

going on this info;

Imagine two 3.5L engines both using GT30R turbochargers. The only difference between the two engines is a different turbine housing A/R; otherwise the two engines are identical:

1. Engine #1 has turbine housing with an A/R of 0.63

2. Engine #2 has a turbine housing with an A/R of 1.06.

What can we infer about the intended use and the turbocharger matching for each engine?

Engine#1: This engine is using a smaller A/R turbine housing (0.63) thus biased more towards low-end torque and optimal boost response. Many would describe this as being more "fun" to drive on the street, as normal daily driving habits tend to favor transient response. However, at higher engine speeds, this smaller A/R housing will result in high backpressure, which can result in a loss of top end power. This type of engine performance is desirable for street applications where the low speed boost response and transient conditions are more important than top end power.

Engine #2: This engine is using a larger A/R turbine housing (1.06) and is biased towards peak horsepower, while sacrificing transient response and torque at very low engine speeds. The larger A/R turbine housing will continue to minimize backpressure at high rpm, to the benefit of engine peak power. On the other hand, this will also raise the engine speed at which the turbo can provide boost, increasing time to boost. The performance of Engine #2 is more desirable for racing applications than Engine #1 since Engine #2 will be operating at high engine speeds most of the time.

i think im looking for something in the middle , i want faster boost responce but the engine is often at higer rpm so i dont want to loose too much top end . so a hot side a/r of .67 should be faster boost than the .72 i currently have on the garret without really loosing top end a just .6 bar

thanks , yest its still stock cams . why would the smaller turbo not make as much power at the higher rpm , i thaught 10psi is 10 psi regardless of the turbo thats making it.

 

i thaught the 4088 was over kill. i can understand it making more power at higher rpm on a big single converted car running 20+ psi but i would have thaught a small turbo that can make 10 psi up to the redline shouldnt cost power.

 

not questioning you , id just like more detals as to why this would be for my personal knowlage base

It's not that simple. Maybe an easier approach, what A/R do you have on the 4088 currently?

Higher lift cams will not help spool, they will lower it but provide better power at higher rpm

Don't forget - turbo change = remap.

I'd go with a Garrett 60-1/T04S journal bearing turbo - around US$880

hey dude slightly off topic what are u running now? am i right in thinking the xs t61?

hey dude slightly off topic what are u running now? am i right in thinking the xs t61?

The clue is in the first post.

yea well there a new fual pump wastegate and injectors too so i have already spoken to ryan about the re - map. just wat to get the turbo right, i just want a cheap one that i can replace like for like after evry season

ok so.. after much reaing and swatting up im thinking ill need something with;

hot .63ar

cold .70

4" inlet

2.5"out

t4 flange

3" vband.

does that sound about rite?

ok so.. after much reaing and swatting up im thinking ill need something with;

 

hot .63ar

cold .70

4" inlet

2.5"out

t4 flange

3" vband.

 

does that sound about rite?

Is the T4 manifold divided or undivided? That will effect whether you need an T4 divided or undivided turbine housing, this will also effect which AR to go with.

The rest is fine.

im 90% sure that its a divided manifold . ill take it off and check . if it is divided what should i look for ? and if its undevided what should i look for , thanks nic

confirmed it is a divided manifold

You'll want a divided T4 turbine housing in that case. What size turbo are you going with?

im thhinking something with a .68 hot and.70 cold . id like maybe a .63 hot but i dont want to lose my top end . its confusing stuff for me

the gt35s look like they have the spec that would be good for me but all seem to have t3 flanges