76 replies to this topic

[Bumblebee]

I'm not looking for opinions but more looking at the facts I.e people who have got this fitted or people who have had this fitted in the past? Thanks

[jameso]

Not many. I would say if you want to go beyond stage 4 you would be well served following a similar build to the Dave H/Simba car?

[MrSimba]

28/67GTX is (in Scoff's opinion) the perfect matched turbo for the Z20LET/H

 

DaveH held the power back at 410bhp / 400ft lb though there is no doubt that 430+bhp is there should you want it.

 

having been out with Dave - who is a very skilled driver - a VX with 400bhp is a very very very fast car, one that very few people could exploit to the full, me... It would be in a hedge within a couple of miles!

 

the 28/67GTX will give you an immense power band to play with though Dave himself will tell you he 75% of the time runs the car at about 290bhp and lower torque.

 

I'd speak with Scoff Aimy, you know him well & he's mapped Garretts on dave's & Zach's and many more on ZLET astra's / Corsa's so really knows the set up well & more importantly knows the drivability of the turbo's matched to the engine.

[MrSimba]

& for an honest opinion from some one who has been there before, stay at stage 4!

 

your looking at about £9k to go from where you are to 400+bhp with manifolds, ECU, Turbo, ect & the extra power will find ANY shortcomings within your engine or drivetrain.

 

At this level of tune it is so finely ballanced that the slightest variable will mean your car is off the road at best, off the road with a substantial bill at worst!

 

Both Zach & I reached a point where we just said 'I'm not pouring any more money into it...' the fun had long gone, which is a real shame as we both had a genuine passion for the little plastic cars!

 

So yes power is addictive, so is modding but your stage 4 will be reliable day in day out, all bets are off with another 100+ bhp!

Edited by MrSimba, 30 September 2013 - 09:20 PM.

[Bumblebee]

The turbo you mention simon is that similar to the gt2871r? I'm not looking for anymore power just looking for improvements on my current setup and I believe the Garrett would e more efficient compared to the k04.Think id kill myself with 400hp

[MrSimba]

GT28/71 is the 'non' GTX version of the 28/67 - the GTX will spool 10% faster and for about 10% further than the non-GTX version.

 

If your not looking for any more power just to improve (immensely...) the drivability of your current set up then the answer is simple... Standalone ECU!

 

GeorgeBC is the man you need to speak with, he went stage 4 to stage 4 with Adaptronic standalone, this is your way forward definalty if you dont require more than 310bhp or so.

 

& at any point in the future if you do the ECU & loom is already there!

 

Speak to Scoff & George!

[siztenboots]

I have a very nice stage 5 map here ready to go , in the grand scheme of things spend the money on the GTX28/67 much better torque delivery. Or you can go hybrid K16 which is another nice option, keep the existing manifold and exhaust.

[GeorgeBC]

Aimy like I said at the weekend you need to drive some one else's car but the problem is that no one has that setup so you have to accept that you are going to have to take a risk. If you can be bothered to drive down to cheshire you can drive mine to see how it compares to yours before you part with any cash. You will also see a cold start etc.

[Nev]

Ian (Danger7) has a GT2871 in his car, limited to about 350 BHP. It was the fastest accelerating car I got into during the National even though he was limping it a bit due to a weak boost pipe.

 

I have the same cold side as a GT2871 on my car, it's a good size to match the engine and the smaller hot-side of the GT28 will (in theory) spool up faster due to it's smaller size. All in all the GT2871 is a good turbo match for a 2.0 Litre engine, particularly if it can rev safely up to circa 7300 RPM safely.

Edited by Nev, 01 October 2013 - 08:49 AM.

[Nev]

Dup post.

Edited by Nev, 01 October 2013 - 08:37 AM.

[Bumblebee]

One company told me not to bother with the gt28 as I would get a lot of turbo lag but then again I hear different stories so it's getting a bit confusing. Anyone got a boost plot? Maybe it just depends on who maps it?

Edited by Bumblebee, 01 October 2013 - 08:50 AM.

[Nev]

One company told me not to bother with the gt28 as I would get a lot of turbo lag but then again I hear different stories so it's getting a bit confusing. Anyone got a boost plot? Maybe it just depends on who maps it?

 

A boost plot won't indicate lag really, comparing the difference in RPM between boost plot to torque will indicate lag providing the RR driver wellied the car and the rollers weigh roughly the same as the car itself. 

 

Lag really isn't a huge issue to concern yourself about, unless you are caught with your pants down at 2000 RPM and you try to welly it. In practice if you are driving fast your revs will be between 3500 and 7000, and then there will be virtually no lag (ie 1/10th of a second or some such).

Edited by Nev, 01 October 2013 - 09:18 AM.

[Bumblebee]

Maybe I used the wrong phrase "lag" what I was meaning for eg if my current turbo kicks in at 3k (can't remember exactly) will the gt28 kick in later I.e 4k? I imagine the gt28 won't kick in as strong as the little k04 which won't be a bad thing I guess?

Edited by Bumblebee, 01 October 2013 - 09:11 AM.

[Nev]

On the whole you are right in your assumptions, but as I don't have that turbo I can't really comment on the exact rpm it will fully spool at. Mine kicks in fully at 4500 rpm, so yours (which will have a smaller hotside) should kick in lower than that.

Edited by Nev, 01 October 2013 - 09:21 AM.

[Bumblebee]

I guess this turbo on a 300hp car is a bit unknown territory really

[Nev]

Yep, there are no more "stages" (ie kit parts) from that point on, it's upto the skill of the mechanic to evaluate what does and does not need doing and what the effects (positive and negative) might be.

Edited by Nev, 01 October 2013 - 10:08 AM.

[slindborg]

ftr, boost isnt really 'on' or 'off'

 

Just less or more

[FLD]

ftr, boost isnt really 'on' or 'off'

 

Just less or more

 

Surely there's a factor of on / off where the compressor wheel is moving an amount of air (in a givien efficiency) which is different to what the engine is 'drawing' in.  If the engine is pulling more air than the compressor moves then its off, once the compressor moves more then its on?

 

Unless you go for VNT or VGT then its ON ON ON!

[slindborg]

Its all just pumping losses (or gains when the compressor it doing better than the engine can)

 

 

[Nev]

Surely there's a factor of on / off where the compressor wheel is moving an amount of air (in a givien efficiency) which is different to what the engine is 'drawing' in.  If the engine is pulling more air than the compressor moves then its off, once the compressor moves more then its on?

 

Yep, that how I understand it, it's a closed loop feedback circuit. However, remember that once it's "ON" fully the wastegate should open to stop the feedback system escalating infinitely.