What would you do with £3000

[1975DCS]

2871R hmm much surge potential problems if not setup correctly. You'd have to use stock cams with it to get best results.

3071R is allot better for the S2 and 450 bhp on a good setup boost between 2871 and 3071 still better than RS2 and you'll be hard pressed to tell the differnce.

Only problem with 3071R is fitting can be a b*tch

Isn't the 2871R not the better turbo for an otherwise stock engine? Can fall well within 350 BHP and 500 Nm safe side with the less lag possible?

The 3071R is maybe better for overall characteristics but does require more modifications right?

Can someone please explain what surge actually means? Or translate this in Dutch (or German) for me?

[1975DCS]

Less laggy = more torque
Torque kills the standard rods.
Wait for the banana rods picture.............

Is that really the case? Yes ofcourse most torque is usually found in the lower midrange. And yes a smaller turbo will do good in that range... But a quick spool up does not mean more torque, only torque coming in sooner.

Simple example S2 and RS2 turbo, RS2 is more laggy but also has more torque especially in the mid and midhigh range...

[S2central.net]

This is NONSENSE guys... You only need worry about custom conrods when you want to achieve torque in excess of 550-600Nm. Yes - an RS2 turbo can be mapped to generate those sort of rodbending numbers, but it can equally be setup by the likes of MRC to run at a more modest 500-550Nm giving stock rods some health margin.

There is perhaps some gain in custom rods (and pistons) if they are substantially lighter than stock items... but only if this is accompanied by a lightened and dynamically balanced bottom end including crankshaft, flywheel & pulley... Work for I5 balancing experts only (eg Basset Down Balancing).


Paul

[Ross]

I guess it really depends what you've got right now and whether that £3k is for the engine, or needs to include other mods?

I'd personally vouch for the GT3071. If you don't push it to the limit you'll be OK on standard rods, after 4,000rpm mine didn't go over 550NM and I still made 428bhp. I've done some extensive looking into graphs and from what I've seen there really isn't much in terms of lag on the 2871 over the 3071, though I haven't any "real world" experience of the 2871.

If the RS2 spec Coupe is another league, the GT3071R is a completely different ball game - with no rules and it only feels laggy between 2.5k-3k RPM, above that it spools like hell. If you're not looking for 400bhp though I would suggest the RS2 route as it's alot less hassle to fit and it's still very quick! Regarding fitting, the GT3071 has a few niggles but nothing that can't be overcome when you know what to expect.

Ross

[S2central.net]

Agree completely with Ross on this - if the target is for 550Nm (max) and circa 350bhp then the RS2 turbo route is absolutely the best. Thats a turbo, intercooler, injectors and a remap... Samco hoses make for good boost insurance.

Properly mapped, the RS2 turbo is nothing like as 'laggy' as in standard factory trim. I'd keep standard S2 cams if low-mid range tractability / torque is preferred over max revs top-end power.


Paul

[porkkis]

2871 is able to give more hp than rs2 turbo.

I'd say the safe limit is near 500Nm. Just my opinion.

[BRY]

I can't see the point of buying a turbo and then "tuning it" not to work to it's full potential.
Rods are available for £300 a set, with a £3k budget I think these should be included.
New pistons aren't required BTW.

[CHEN]

Thanks for all the imput guys, you are really helping put together what I want. If I do go for the GT3071R (if I do I will put new rods in for safety sake) will a lot of the power be wasted because I have no real intention of changing the intake set up other than an RS2 intercooler?

[S2central.net]

In my opinion yes - the RS2 IC will be a limiting factor...

Word of advice though - get a run in a 3071 equipped car - drive it yourself tooling round town, some mid-range overtaking and a few WOT blasts... Then do the same with an RS2 equipped car. Then you'll feel the difference.

To BRY's point I don't think it is pointless to run the RS2 turbo in a 'detuned' state with a 500-550Nm limit. I for one prefer a fat and flat torque profile - for linear power delivery. I always think these turbos mapped for a massive torque spike in the mid range are a bit odd to drive as those torque levels are reduced towards the redline... and you don't feel a nice linear power delivery.

Just my opinion like... If we could have 1000Nm from 2000-8000rpm then life would be wonderful huh !

Paul

[1975DCS]

If the 2871 has more power potential than the RS2 turbo, than it must be probably possible to get a nice flat 500 Nm+ torque curve and 350 bhp+. Right? This must be the way best method for affordable tuning than? As no major changes are required and probably great suited with stock RS2 parts, like the intercooler or injectors.
As far as I have read (and understand) this gives the spool up of the S2 (or even better) with the power level of the RS2 (or even better). Looks like my choise...

But if I would have the budget for a change in hardware (including rods, massive intercooler, coil upgrade and probably a gearbox) I would go for the 3071 as it seems like the biggest turbo that still makes sense for normal road use...

[Ross]

If you're leaving the intake, it'll add a bit more lag of course but nothing more than what you'd get with an RS2. I can only assume that a big IC will help with those extended blasts, or on hot days, but I didn't suffer too much with the RS2 IC equipped. Though for all I know a big IC could have given me 450 on the dyno, but for the sake of keeping it 'stock' i could live with a possible slight loss in power.

I built my engine with forged rods too, my torque was in the 'danger area' but NOT as high as some with RS2 set-ups on stock rods! I'd advise it for insurance sake though, at least you can be safe in the knowledge you don't have to take the engine apart for a bent rod in the future... I'd say get the whole lot balanced by Basset Downs though if you're taking all rotating parts out, you'll love how it revs so smooth.

[1975DCS]

Oh BTW what kind of boostlevels (at what RPM?) and spool up figures are we safely but potentialy (from a turbo point of view) talking about if we do talk about 2871 and 3071? Or maybe as comparison with figures from an S2 and RS2 turbo..

[Jamo]

I guess it really depends what you've got right now and whether that £3k is for the engine, or needs to include other mods?

I'd personally vouch for the GT3071. If you don't push it to the limit you'll be OK on standard rods, after 4,000rpm mine didn't go over 550NM and I still made 428bhp. I've done some extensive looking into graphs and from what I've seen there really isn't much in terms of lag on the 2871 over the 3071, though I haven't any "real world" experience of the 2871.

If the RS2 spec Coupe is another league, the GT3071R is a completely different ball game - with no rules and it only feels laggy between 2.5k-3k RPM, above that it spools like hell. If you're not looking for 400bhp though I would suggest the RS2 route as it's alot less hassle to fit and it's still very quick! Regarding fitting, the GT3071 has a few niggles but nothing that can't be overcome when you know what to expect.

Ross

Ross why was your old S2 tuned to only run at 550nm when you had SPM rods?

[Ross]

Good question.

Not sure really, there was absolutely minimal backpressure so a drop in torque could have been a result. I must admit, it was a little lower than I expected it to be, hoped to see ~600nm peak. Guess we'll see if the ABY can push a little higher :mischeif:

Another thing was that onthe dyno run it spiked @ 585nm then pegged back the boost in the midrange. On the road you could you see 1.8-1.9bar at at around 3700-3800 which held pretty much to the redline. I suspect it was holdng high 500s in the midrange in reality.

[Jamo]

Just curious as you went through having the rods replaced but running the same torque you could do with standard rods albeit on the standard rod limit.

Seems strange as you had custom rods the turbo wasn't cut loose so to speak.