ALFAGTV6.COM

[Mats]

oil in the exhaust will also destroy the per regulation mandatory catalytic converter...

[ChrisS]

OK guys - thanks for the thoughts. I'll leave it alone then. It's not as if there's a lot of fume and so far, it's not making a mess under the cover as I was careful where I put it.

[ChrisS]

Minor update before the RR session on April 9th - I've finally sorted the drive belt niggle - nothing more sinister than not enough tension it seems. With the 'fixed' adjuster it had before, the belt always had a tendency to try and climb off the blower pulley on cold start. Back when I first tried this setup with the previous engine, it had this problem too, but I didn't realise what it was at the time - I thought the odd snapping/clacking noise was from the blower gearbox as it was a very used one. Turns out it was the belt all along, as the rebuilt blower on this engine did the same trick, but I actually caught the belt in the act of trying to escape this time.

Anyway, fitting a spring/damper style tensioner from some BMW or other has sorted it. There is way more tension in the belt now than I would ever have dared to put in manually, but given the thing can adjust itself, I'm not concerned about it. Belt now behaves perfectly at all times and the slight rising boost one would expect has now appeared, which suggests it was probably slipping slightly before at higher revs. I had always intended fitting one of these dynamic things, but the item that came with the Clio tensioner unit I used wouldn't quite fit, so I made a simple mechanical adjuster as a temporary fix.

All ready for the mapping session now. I'll report back with the numbers (he says optimistically!) in a couple of weeks. I've finally got over chasing numbers, so it'll be what it is, and that'll be that. It drives great, which was the whole point after all. I'll leave the massive BHP numbers to my mate who is building a twin turbo GTA motor at the moment.

Next 'problem' will be the 6 speed gearbox. We've recently seen a couple of these throw off the end of the main casing and spill gears and twisted metal all over the road. So far I think it's only been 156 2.5 V6 boxes, but not totally certain. I managed to blag a 147 GTA box, which has unique part numbers for the casings etc, but I don't know if this means it's any stronger.

I'm in no rush to add the extra gear though - 5 are fine for now.

[ChrisS]

Right, results time. As anticipated due to the low boost figure, somewhat dissapointing. 256bhp/261lbft

Plot attached. Rise in boost at top end suggests it's starting to flow-limit maybe. Advancing the cams a degree saw no change in boost, few bhp more power, bit more torque. It didn't want an awful lot more timing than it had, which surprised me a bit, but it wants what it wants and that's that. I reckon it would take a good deal more boost without problems...if only I could find out where it all went!

I'm going to leave it be and just enjoy it for a while now, but longer term, I might be tempted to have a bit of a fiddle to try and find some of the missing boost. Most likely culprit is probably cams, but before I get to that, I think I'll try removing the charge cooler, or at least measuring pressure before it - I've had doubts about that from day 1 really.

Still, it's driving really nicely after mapping and pulls well enough.

Meh.

[Lancianut69]

Hi Chris,

Nice pics! Thought for a mo you had some neons on board til I worked out what it was!! ;o) Disappointing as you say on the one hand but good to know the timing waqs pretty much there and now you can concentrate on enjoying it while you work out what job comes next!!

Look forward to hearing about the next steps.

Cheers

Darren

[ChrisS]

Well, apropos of nothing much....it's more than a year since my last post on this, and in my usual half-arsed manner I've been fiddling and faffing with it.

Having talked myself into thinking cam overlap was the cause of lack of boost, I put some stock cams back in it over winter. A 6 speed gearbox as well, but that's neither here nor there apart from meaning I couldn't re-fit the charge cooler ans ther was nowher to put the pre-rad.

I was convinced boost had increased a bit with the stock cams.

SO, finally got round to having another day on the rollers and the result was.....more than 20bhp down on before (probably closer to 30bhp actually). And boost wasn't really any better either - maybe a bit but not significant. I suspect I did my test run on a cold damp day when I got a better result.

I'd been prompted to try retarding the cams by a handful, based on the results a chap in Sweden had with his engine, so we tried that - did nothng but make the power worse.

Restored the custom cams and tried again. With the cams timed correctly, power was back to where it was before. We swung the cams a handfull both ways and again, it did nothing but lose power.

Conclusion? It's a rubbish blower. I can't spin it any faster without totally re-engineering everything due to the packaging...and if I was to go to those lengths, I'd fit a Sprintex S5-335 instead of an Eaton M90.

The other conclusion is that Richard Jemison makes a damn good camshaft! I apologise for ever doubting him.

Greg had always tried to talk me into using an MP62...but I'd already made the kit before we 'met' and was wedded to the idea of sticking with the M90 so had one rebuilt/tuned for me at Embree Machine. A very poor choice of both blower and blower tuning company it seems.

Ho hum.

[MR2 Zig]

Which is the bigger blower the 62 or the 90? Is the blower rpm in the right range? Have you tried fiddling with the pulley sizes to adjust the blower rpm?

[Duk]

Which is the bigger blower the 62 or the 90? Is the blower rpm in the right range? Have you tried fiddling with the pulley sizes to adjust the blower rpm?

90 = 90 cubic inches per (blower) revolution.

It really is a shame to see such massive effort return unsatisfactory results.
It definitively doesn't suffer from belt slip?

[ChrisS]

Sadly, no belt slip for sure. Boost is almost totally flat from end to end. A very slight rise at the top as you'd expect really - blower efficiency increasing a wee bit, but it is what it is. Already running at damn near 2 x crank, so rev range is where it should be for an M90 really.

The MP62 is a better blower for this size of engine/level of boost I think. Greg did tell me - just wish I'd heeded the good advice before I wasted $1100 on another M90 really. It wouldn't have cost me that much to re-jig the installation to accept an MP62. Now though, it's too far down the road and I can't face the cost and effort of effectively starting again.

I don't even enjoy driving the car much any more either.

[WhizzMan]

Put it away for a while and pick it up after the summer. You need some mojo to start this project again and you won't get that overnight, unless your numbers come up.

[Greg Gordon]

Keep in mind, even the fourth Gen MP62 is now pretty old. It's a "4th" generation supercharger, they are now up to 6th generation with the TVS. The newest Sprintex units are also at least equivalent to the 6th gen TVS, even slightly more efficient at high boost levels.

To put all this in practical terms, the Sprintex S-210 has the same drive power requirements and delta temps when moving the same amount of air at 14psi as the 4th Gen MP62 has at 10psi.

Time marches on, and superchargers are always getting better. The Eaton 3rd-5th generation blowers were amazing 20 years ago and darn good 10 years ago. Now they are left hopelessly behind.

I have switched to a newer blower for my Spider, and I don't really know what I will do about the V6. I have one V6 kit left with a 4th gen blower. I just can't decide if I will make more, or design a new kit with the Sprintex S335.

Of course the argument for keeping the older MP62 is that with enough work in the heads, plus good headers etc. it can make enough power to break everything aft of the engine, and it's less expensive. The newer blowers can do that without any other mods.

Greg,
http://www.hiperformancestore.com

[75evo]

Greg, how does the sprintex compare to the new TVS eaton in terms of price and drive powr and discharge temps? Looks like the twin screw has the slight advantage.

[Greg Gordon]

I am going to generalize here because there are so many variations of both the current TVS and Sprintex blowers. Assuming two units of similar displacement it breaks down something like this:

Price, the Sprintex is quite a bit more expensive, and it doesn't have a built in bypass valve so that will add to the cost of the project.

Drive power/Discharge temps: This one is darn close, and difficult to compare with total accuracy because each manufacturer provides charts in totally different formats. Below 10psi the TVS seems to have a slight edge, 10-15 they are too close to call. At higher boost levels the Sprintex has the edge, there are quite a few running at 25psi, I know of no TVS running that high.

Weight, the Sprintex is heavier. Surprisingly so.

Size, the Sprintex has a big advantage here. For a given displacement, it's external dimensions are a lot smaller. This is actually a pretty big factor on the Spider as it's short enough to bolt the throttle to the back of the blower a la Buick. This makes it super quiet without a lot of extra plumbing between the throttle and the blower. This is almost impossible to accomplish with the TVS on a Spider.

Greg

[gtv-racer]

why don't you tune the supercharger itself. I read in Gregs book it can be done at Embree machining. Don't konw what the costs are and what the boost rise is for an m90 unit..?

EDIT: m90 unit @20.000rpm 0.96 bar (think it's the 5th gen) more then enough i think


What exactly do the change then. Only other bearings or do they mill up the diameter of the charger where the rotors are for the extra heat....? Maybe you can do it at a local shop... Calculate the temp rise and so the extra delta T. Convert it into mm and there you are. If it needs to be done....?

[Greg Gordon]

Because he bought from them, and it didn't come back as advertised. I have no explanation for that as I have had good experience with them in the past.

Greg