Hi Jonty, Maxdax - sorry for the thread highjack!

well, firstly because Mark Shead has said so on several posts, secondly his various dyno plots show that is does spool better compared to my results, thirdly because of this video

https://www.youtube.com/watch?v=q3PfyeLALPM

and forthly because the borg warner matchbot program says it will.

i found the matchbot program is really enlightening. you can tell it what boost you would like to see at what rpm for a given engine size and you can then dump those figures onto any of thier current compressor maps which, of course, also gives you the speed the turbo needs to spin at for that boost at whatever air flow is required. it then will work out how much power the turbo shaft needs to develop and which turbine is capable of making that power at that turbo speed. you then 'tune' the lower graph to ensure they have a turbo with matched turbine for your situation. the 7064 seem to look better than a 7163 for a 2 litre engine in terms of early spooling.

im not saying that the 7163 is a bad turbo for a yb - far from it. its easily the best turbo i have used but i have no experience of anything newer than a TT38. it's certainly makes my car quick and almost scary from about 5k onwards and would be probably quite well suited to a typical 7 2wd in so far as the boost doesn't come in with a kick like a t34 does which can easily light up the back wheels. i think the 7163 might be be a good track turbo for a high revving 7 but less so for a road going 7 with a 3.6 diff. 5th would never get into the full spool unless you're doing 90mph as you're typically trying to keep it over 4500 to make it work. 7's aren't usually used as high speed motorway cars so why have gear ratios / turbo which is suited to that environment? i haven't looked at the 6258 or 6758 in matchbot but i think they would look better for a road 7 than a 7163 is.

I've got a 4.4 diff, an 800kg car with 8:1 comp, home ported head, bd15/16 cams. i dont know how much impact the cams have but in my limited understanding of the situation you dont need std short duration cams with twin scroll and you benefit from the higher lift & longer duration. happy to be corrected on this however if someone thinks that my cams are impacting on my spoolup. i have played around with the cam timing +-5 degs on each one from a start of 110 / 110 with little impact.

It's also possible that a tuner would get better spooling results than i did. it has been on a rolling road but the guy didnt really know much about it and said that there was too much noise for him to use his det cans?????? so he left the timing safe at 5 degrees AFTER tdc when it was on boost - waste of time imho. maybe someone who knew what they're doing could improve spool by adjusting cams / ignition.

I'd post up the data log if i could understand how to do it but it shows the following:

in 4th and flooring it from 1765rpm we took 5.5 seconds to get to 4904rpm with boost as follows:

3500 - 14.3psi
3709 - 17
3813 - 19
4000 - 22
4300 - 28
4700 - 32

i also tried holding in the brakes to load it up but that didnt improve the boost figures

by contrast, the engine in the vid seems to be making 480lb ft at 3500 at 2.6 bar @38 psi