400 odd HP turbo selection

[green_rs13]

if you wanted 380/400 odd BHP what turbo would you buy?
the aim of the game is a nice responsive turbo with a broad power curve so it gives nice driveability. over 400hp seems to be where problems start, so staying under this should yield reliability (he hopes!!).
id like to stay internally waste gated and low/bottom mounted, the fabrication side of things is not really an issue.

ive been thinking of the EFR 6758 with the .64 T25 fitment single scroll rear housing. This should bolt upto an off the shelf s14 manifold which should make my life easier as I would just have to fab up a down pipe and inlet etc..
. but I see they also do a .80 T4 twin scroll, i assume this would give it more grunt 'up top' but am unsure what would be happening lower down the RPM scale. the internet seems to be awash with build threads of people fitting these but then never commenting on how they perform.

I also see talk that the larger EFR 7163 (which has the T4 .80 twin scroll rear housing) spools the same if not quicker as the 6758 but does not 'top out'. this is obviously a larger turbo and exceeds my power goal.


or i could get a GTX2867 but these are well over a grand and ive had crappy garrett bearing cages fail on me in the past. A2871r just seems like a dinosaur these days as do the TD04, TD05 etc..

ive got rb25 gearbox/forged engine /720's etc.. so am 'good to go' in that respect.

where would you put your money and why?

[scythe]

Delete**

[ANDY black s13]

zepplin has got to be the man for this question I think

[green_rs13]

GTX2867 gen II A/R .86 best turbo for Sr20, quick response full-boost 3500-3600obr/min.


My setup 370hp/495NM , stock manifold, ID1050X injector,1.35bar boost, Link Ecu, BC stage 2 cams

I guess the larger (.86) rear helps with the top end where the other models with .64 tend to suffer with top end issues like boost creep. also nice to see people using the stock manifold.

zepplin has got to be the man for this question I think

anyone is free to chime in. that's why I thought I would throw it out in the open.

[hooky]

GTX2867 gen II A/R .86 best turbo for Sr20, quick response full-boost 3500-3600obr/min.


My setup 370hp/495NM , stock manifold, ID1050X injector,1.35bar boost, Link Ecu, BC stage 2 cams

Agreed, the GTX2867 is probably the best option for a responsive 400 ponys, and I cant help but notice the above setup at just 370hp must be extremely conservatively mapped! either that or the stock mani is worse than i thought

[polcastrol]

g25-550 https://www.turbobygarrett.com/turbo...series-g25-550

[green_rs13]

Agreed, the GTX2867 is probably the best option for a responsive 400 ponys, and I cant help but notice the above setup at just 370hp must be extremely conservatively mapped! either that or the stock mani is worse than i thought

took me a while to click but he uses mixed measurements. HP and NM instead of HP and ft lb's or kilowatts and NM. I was like 500 ft lb of torque WOOWWEEEE im getting one of them wee turbo's!!!!

going by his figures he is making peak power at roughly 5300 RPM (power'KW' * 9549 / rpm) so that's 365 ft lb's of torque


I have seen the new garrett stuff but they are like £2000 and that is a really big number to swallow.

[Actual_Ben_Taylor]

Haven't looked at turbos in a while, but I'd definitely go top mount on a nice equal length manifold and external wasregate.

The GTX2867R Gen2 with a Tial exhaust housing would be a great setup.

[green_rs13]

Haven't looked at turbos in a while, but I'd definitely go top mount on a nice equal length manifold and external wasregate.

The GTX2867R Gen2 with a Tial exhaust housing would be a great setup.

I just prefer internal gated turbos, they seem like 'fit and forget' solutions. external setups seem to just take up loads of space and cause people problems. but then EWG seems to be the only way to not have boost creep issues on a garrett jobbie.

from memory the teal EXG housing has a A/R of something like 75 so slap bang(ish) in the middle of the garrett's usual .64 and .86

[zeppelin101]

Twin scroll will help get the thing going if you were to go with the 6758. Hard to say how much of a difference it will make, you're usually more restricted by the inertia of the thing in lower gears so probably wouldn't see the impact until 4th or 5th of twin scroll, especially with a short diff ratio.

You'll be sensitive to the exhaust manifold. In a lot of instances the twin scroll benefits are reduced somewhat by the manifold design to unlock peak power where the runner volumes are quite large. All the little things like that add up to reduce responsiveness and low end torque. That's where the benefit of the stock manifold is to be honest.

It sounds like you're prioritising low-mid torque over peak power?

Are you doing anything with cams? Lengthening the intake is bad for low end, wants more boost up top to compensate if you stay short. Longer duration exhaust would help with recovering a little at peak power, still a trade-off at low speed though.

[R3K1355]

Garrett's new G-series turbo's are just hitting the market, someone needs to be brave and give one a go.

[green_rs13]

Garrett's new G-series turbo's are just hitting the market, someone needs to be brave and give one a go.

The 'Bog Warmer' turbos are about a grand, think the t25 housing 6758 was £950 (ive not priced it with the twin scroll rear) and the 7163 (twin scroll t4 rear) was about £1150 when I enquired. ive heard rumours that the G-series is going to be about £1700.


ive got a few fake Tomei Expreme mainfolds kicking around so would either use one of those or get an APW one or even fire up my tig welder and make one. don't think i even own a stock cast manifold anymore.

i just figured that my power goals were pretty tame compared to most these days so would see if i could spec a setup that gave a dyno graph with a good amount of 'land' on the left hand side and not just be fixated by whats happening on the right side of the graph, if it tails off but still nets me 380 HP then i would be happy. I'm on stock rockers/lifters/shims and tend to shift gears when i feel the car stop pulling and not when its on the rev limiiter. i guess you could say ' i want my cake and eat it'. i just didn't want to sacrifice too much low down/mid range for top end.

I planned to stay with the stock cams (240 duration) and VVT for low and midrange. bigger cams tend to beat the VVT sprocket to death.

big turbo cars with all the power 'up top' are a pain to drift as they often fall off boost meaning you have to do monster clutch kicks to get back into the power band. This is when your drive train explodes.

[zeppelin101]

I'd look at twin scroll 7163. The 7163 seems to behave similarly / slightly better than a 0.64 6758 in terms of torque @ rpm and transiently but gives a lot more at the top. You would definitely nail 400hp with that turbo.

Plots below are from an STI, but still help to demo the point...




A twin scroll 6758 probably won't be much better, only because there is a bit more imbalance between the compressor and turbine wheel sizes so it won't get going as quickly ironically.

Not sure if it'll work out cheaper but Full Race are offering some cash off 7163s at the moment too.

Agree on cams, a slightly longer exhaust would be nice with the twin scroll but small benefits to be had.

[green_rs13]

It just seems wild that a bigger turbo comes on song sooner. seems to go against the usual trade offs. id seen that perrin performance article before and it does look tantalizing. it was that which led me to wonder what the twin scroll 6758 would do, id overlooked the mismatched aspect of the TS 6758 and that it may be a burden.

I was looking at the driftworks s15 that has an externally gated 7064 and shuddering at the thought of squeezing it all into the space hence why internal gates were my preference (that and it would save a heap of cash).

im sure the stock cams are both 240 duration, rn14 pulsar is like 248 exhaust and has more lift but is designed for solid lifters, next are tomei/264 and I think hks step 1 are 260.
annoyingly I have a 248 NA inlet cam shaft, which is why ive been soley tempted to stick a pulsar EX cam in and have some pretty mild cam upgrades.

[zeppelin101]

Black top SRs are 190 @ 1mm on both ends. I don't like cam companies talking in seat to seat duration it's not relatable to when the cam is doing some real work. Kelfords mildest offering and BC stage 2s are about identical (218 ish @ 1mm, HKS step 1s are a little milder but not by much, 210 or so @ 1mm? Not wild by any measure but starting to get long for low speed get up with half decent ports, much longer than this and it all becomes about much higher speed at the expense of bottom end.

For the turbo response there are a few things at play, one of which is the relative efficiency of the turbine to compressor. In theory the inertia of the 6758 will be lower than a 7163 but if the relative wheel efficiency is lower then it won't matter as much because the turbine can't extract the work it needs to drive the compressor demand.

The 71mm compressor is pretty decent too, it's got a handy amount of surge margin and a lot of breadth that works well on a 2 ish litre engine for this level of performance. The 67mm compressor doesn't flow as well as the Garrett counter part but as a unit the 6758 will usually make up for it a little because the turbine size is that much bigger than a GT28 that it hangs onto peak efficiency a bit longer.

Internal gates are fine if big enough and you're running enough boost. Usually have problems when the turbine isn't being pushed hard enough.

Funnily enough DW would probably have been better off with a 7163 as well Only because there is more surge margin on the 71mm wheel versus the 70mm!

[green_rs13]

when i saw DW strapping the turbo on I straight asked them if it was a 7163, I then looked at the info for the 7064 to try to figure out why they went with it.

think I will go for the 7163 twin scroll internally gated t4 .80 A/R
then keep the stock cams.


this is the BorgWarner site with loads of info should anyone be searching in years to come
http://www.turbos.borgwarner.com/fil...ical_brief.pdf

[zeppelin101]

Look forward to hearing what you think - it's a setup I'd be tempted by too even for more modest power!

[green_rs13]

just give me a while to find some money down the back of the sofa.

[Scottie]

I know it's not exactly news, but after lots of research and being in lots of cars I went for the 2871 0.64 with 256 poncams as it gives great response and a huge powerband. All depends what you want to use the car for I guess.

People tell me they regretting moving up to a larger turbo than the 2871 because they just lost that instant go it seems to provide vs bigger options.