having spoken with both Craig and Mano at Turbo dynamics, I have a turbo dilemma

1) GT28R with larger compressor wheel
2) GT28RS with standard 0.64
3) GT28RS with standard turbine, but larger compressor wheel

In my ignorance of fine detail on turbos, is No3 just the GT28RS with the 0.86 compressor?

This is all based on the fact that my existing GT28R is still making increasing power at the redline (although the boost has always dropped of by then)

I will be able to run high boost (forged pistons) and I DON'T want too much lag. Current setup gives me decent boost by about 3,000 rpm

So, I'm looking for 3,000 - 3,200 spoolup (remember I have yet to fit a straight induction mod, and I'll certainly be having C&B cams). I also want boost all the way to the redline (although I accept that a bit of drop-off is safe) Whilst I'm looking for 330 - 340 bhp now, I may want more later.

My current preference is no. 3, as I can learn to live with 200-300rpm more lag, and the cams and induction will pull out anything above this

Any thoughts from the usual bunch of turbo-nutters?

I'd go for number 3 Nigel, possibly 2 - but not 1. Looking at the unichip thread graphs it does not look like the R units spool up that much quicker than a 0.64 RS, and they dont develop the same power. the turbo of choice is definately an RS if you'r going to boost it up and really get an RS going, which you'll be able to do!

The GT28RS 0.86 is on the turbine side i.e. you have the choice of .64 or .86

If you can wait a few days Nigel it may be worth seeing what Frag's Unichip remap comes up with as he is running option 2. I would say if you can run more boost then the standard .64 RS is definately good for 340-350bhp.

not a turbo nutter but reacently done alot of calling around on turbos etc (spoke to mano also)

my oppinion is 2, because you will still be able to run enough boost and power to kil your engine and have quicker spool up.

@340/350bhp i dont think you are pushing the 0.64 too much and i am confident you will have more to come if you want it.

just my oppinion, probably boll**ks but hey

I've got option 1 and there doesn't seem to be any differences with that and a standard R.

If I had to buy another turbo it'd certainly be option 2.

id vote for number 2 as well nigel as while i know some are running the bigger turbo i think its a bit laggier. An ideal compromise would be the .64 housing 28rs with the same exhaust side as the 28r but i have a feelign that would be very pricey from TD if they made it up.

What have they suggested as you could use their advice and then buy it from ATP, which is a bit sly but the money saved would go towards forged bits surely

Nigel, I think you may struggle to get spool-up less than 3500rpm with the (0.86) GT28rs.

However its a very smooth turbo, which makes the car feel more normally aspirated than turbocharged if that's your thing, and it will allow more headroom if you really want to start pushing things boost wise once you have your forged pistons.

The only slight caveat is that with the standard injectors 350bhp is going to be right at the limit with this turbo, maybe a bit more like flea's results but not much.
So if you are going to push the boost further, and you can run 1.6 even 1.8 midrange with this turbo, then you are going to run into this issue.

So that means larger injectors and then probably either the latest Unichip (Fergies results not withstanding) or Motec/DTA etc

Another issue with 350 bhp + is the concern about the strength of the Coupe rods if you are not going to upgrade those as well.

so you see there's a few obstacles to runnign more than 350-360 bhp which you will almsot certainyl get running a GT28rs with those mods I would have thought.

So,.. if you are not going to go over the 360bhp barrier, and keep her more reliable, then probably the GT28 rs (0.64) will get you up to that limit, be able to keep your injectors and give you 3000rpm spool up....hmmm decisions decisions!!

regards

Joe

ps remap on Monday next week, so will have a clearer idea then

Hi Nigel, good morning.

A few more thoughts this morning...

As you are possibly running in TOTB, the (0.86) would make possibly the faster drag strip turbo, it would be easy to keep the turbo on the boil, and you may find the torque curve slightly better 6000rpm+ which may net you a few tenths, only speculating mind you.

The other issue is the clutch, the smaller versions will be harder on the clutch, and you may then have to consider a paddle to cope with the demands of the harder boost delivery.

Joe

Choice made, money paid - lets just say I haven't "followed the crowd"

come on nigel... what did you get?

I've accepted a bit more lag - will probably see 3,300 - 3,500 spoolup. It would almost certainly be higher than this on a more standard car, but the headwork, cams and straight induction should bring it back to more acceptable levels.

However, I now have a turbo capable of delivering 380+bhp, although I have a feeling that I won't get within 30bhp of this, due to other restricting factors, like clutch, injectors and rods (although I think I'll fit 16VT injectors for the Unichip remap)

Any guesses?

GT28RS 0.86
GT30R

??

GT2871R or 3071R

Cyclone got it - GT2871R

Lagtastic choice Nigel , but with your additional mods you should compensate for that somewhat, should also give you more bhp potential and make the 1/4 mile times improve.

Jules.

gt2871r Stichl has one of these fitted to his coop it has 396 hp @ 1.4 bar at redline i think around 1.6 midrange although he told me there is nothing before 4250 rpm even with the cams it will be slower spooling than a .86 rs around 5-600 rpm ,stichl runs a 2.75 turbo back exhaust though so if you go 3 inch you might gain 200

Jesus that is quite laggy!!

I see base boost at just over 3000rpm hopefully more when i get the straight induction pipe someday but i have tyres and bits to sort before then!

Cool Nigel , I think you've suprised all of us here! , thought you were after as quick spool-up as possible

Well, you should be able to push some numbers with this turbo, and on the strip will have you nicely into the 12's I would have thought, be interesting to see what you think it is like for track and road driving as its directly interchangable with the GT 28rs.

Which GT2871R have you gone for?

Joe

I would have gone for the RS .64 in all honesty for you nigel as i dont think they max out easily even with more mods unless u go for more cc's...

Well, I spoke at length with Craig and Mano from Turbo Dynamics. I've been informed that the 2871 is no more laggy than the 28RS, and in some applications could spool even earlier (we discussed all my mods and the effects on spool-up)

I realised from the start that I was going to get some more lag than with my 28R. However, I've also been told that the 2871 will drive more nicely at more modest boost levels, with big power available from low(ish) boost.

I remember getting the 28R and finding that spool-up had moved from 2,500 to 3,000 and worrying that I wouldn't like it. Whilst I still occasionally get caught in the wrong gear, I've got very used to it. I imagine with the 2871, I'll just have to use one gear less when expecting to make a quick getaway.

When I sat down and thought about it hard, I realised that I wasn't necessarily looking for early spool-up - I was loking for nice off-boost characteristics for when I'm trundling in traffic at sub 3,000rpm. Keeping my existing turbo would have had no positive effect on this at all. All of my improvement in off-boost driving will come from the two main mods of the rebuild - headwork and cams. A Unichip remap (maybe with some 16VT injectors) should see a tweak in low-end tractability too.

However, I decided that the point where I enjoy the car the most is the massive surge of midrange to top end wallop. I love the way my car is still making more power when it reaches the redline. I love the way it howls after 4,000rpm. I love the way it continues to accelerate as hard after 100mph as it did under 100.

The GT2871R is just going to give me a load more of what I already liked, but from a 500 - 750rpm narrower band.

If only I could afford the forged rods, I'd be able to up the rev limiter with a custom G-Tec chip. However, I'm hoping that my standard rods will be good for 350+ bhp, which I'l be pretty happy with. At least I have the capacity to go for more bhp if I fancy risking it.

Can't wait now - decided that the full respray can wait until after TOTB - I need the car back ASAP to get some miles on it then take it for a remap.

Agreed offboost driving is a good bit of the experience of a coop, i noticed in teh last 2 days from gtec1 - gtec2 that off boost and sub 3k pickup is much better and smoother and even idle has improved as well for me

Just have to find out what teh fuelling is like on higher boost as i still running medium boost of a maz spike of 1bar settling to about 0.8/0.9 when movign quick

Nigel, my cars in the middle of its remap, and at 345bhp at lunchtime today, a very hot day. I'm hoping for 350bhp come when she's finished , and that's with the smaller GT28rs.

In all honesty with the GT2871r, I think you will find it easy to get 350bhp+ !!

joe

I'm really not having a good time of it.

Having got the actuator problem sorted, my 3071wg has decided to give up the ghost

Most likely reason is bearing failure (cause of which to be assertained) but the out come of which is a compressor wheel bashed to pieces thanks to touching the housing. Seems to also be a fair bit of play in the shaft. Anywayz will be going to TD for them to diagnose / fix / replace etc

Not gonna moan much (yes I'm depressed, but hey I'm still here!), but the car was beginning to run very well. 1.1bar equated to 280bhp and each extra 0.1bar was worth aprox 20bhp on top

I could see boost at very low revs, but only about 0.5bar up to 4000rpm where it would quickly increase to a bar by 5k and then go wild to the red line.

Yes, that seems like a small HIGH POWER band, but if I increased the rev limit to aprox 8k, it would transform the car. The other interesting thing is, even though its low boost low down, the car is still producing the same power as my hybrid was at 1.3bar at the same revs.

Fergie, really sorry to hear the news , very unusual to break a roller bearing turbo indeed, although I believe JohnS did the same to his. It will be interesting to hear what TD have to say.

I found that increasing the boost beyond 1.4bar with the GT28rs (0.64), did not yield any appreciable benefits.

How did you find controlling the boost at 5000rpm plus? as the 2871r and 3071r hit their 'sweet spot' and take off!

Was the mapping going fine as well?

joe

I have read that as well.

Im sure i read something on one forum saying that the highest efficient level for the rs 64 was 1.5bar and as i dont intend to mod my car that heavily i will never push over 1.3bar ever, at the moment i tootle about on the lowest boost possible!

I have heard of the odd GT turbo going due to oil starvation but it has to be pretty severe to cause it due to their design they can cope with it better than a journal bearing, although not advisable i did know at least 1 of the 2.4 guys blew a turbo up but i thought Mav had as well, maybe a different one.

A coop that would rev to 8k would sound very sweet me thinks can the bottom end, even uprated take it though as i havent heard of it before in the coop world...

Im hitting the same boost as fergie but about 1500rpm lower! :surprised: now that is scarey and shows what the internal mods alone are enabling you to do

Hi,

I have a GT2871R (with big compressor wheel) and 0,86 turbine installed... below 4250rpm you won´t find "any utilizable power"...
I have done head work, too, plus a 3"- Pipe +2,75" exhaust + sport cat, short induction and so on...
I do not know the effects of a CB-cam.
But I think that you will gain a similar result to mine...
To get 396HP I had to adjust the boost to 1,7bar overboost and 1,6ar redline...
FOR SURE you will get better results with a GT28RS in lower revs...
May be the 0,64 housing would be a solution. But then you could get problems with the exhaust temps because of back pressure
Juergen

The plot thickens

Taking the turbo off, I've noticed a hairline crack just to the left of the collector. This may explain my lack of boost that I was blaming on a soft actuator

Not sure how easy it will be to weld insitu and I'm not too sure about taking the manifold off when aircon is ontop of it!