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 22 Posts Member #: 5451 Member Melton Mowbray |
15th Jun, 2009 at 07:09:07pm
Hi all,
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 8604 Posts Member #: 573 Formerly Axel Podland |
15th Jun, 2009 at 07:16:59pm
It's been done before but I don't know if they have been used in anger:
Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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22 Posts Member #: 5451 Member Melton Mowbray |
15th Jun, 2009 at 07:34:50pm
On 15th Jun, 2009 Paul S said:
It's been done before but I don't know if they have been used in anger: http://www.turbominis.co.uk/forums/index.php?p=vt&tid=135934 I'd use a 12G295 head and leave the pistons as they are instead. Thanks for the reply Paul, I was going to use a 1275 head, chambers worked, etc. And it says in the description it can sit happly at 9.5 CR with a Cooper Head, so not sure. And I am only hoping to run the standard pully, etc, at about 8.5 CR (?). |
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8604 Posts Member #: 573 Formerly Axel Podland |
15th Jun, 2009 at 07:42:46pm
Flat topped pistons and the 12G295 give around 9:1.
Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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 10020 Posts Member #: 1456 Mongo Barnsley, South Flatcapshire |
15th Jun, 2009 at 07:57:43pm
Only reason I can think of is ease of installation, due to the kits from the likes of vmax and jonspeed. Also the fact that the M45 is readily available at a good price.
If something is worth doing, it's worth doing half of. |
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8604 Posts Member #: 573 Formerly Axel Podland |
15th Jun, 2009 at 08:14:33pm
On 15th Jun, 2009 minimadmotorman said:
Only reason I can think of is ease of installation, due to the kits from the likes of vmax and jonspeed. Also the fact that the M45 is readily available at a good price. The problem for the 998 is that you need to slow it right down to get it operating in its comfort zone where it will produce power producing boost. There are plenty of 1275s fitted with these kits that are running 15-20psi boost, but at high inlet temperatures that means that the air is not carrying the oxygen it needs to make power. Plus it induces detonation that will destroy pistons. The same kit on a 998 is a timebomb. Unless you can get or make a crank pulley much smaller than standard, then it will end in tears. Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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22 Posts Member #: 5451 Member Melton Mowbray |
15th Jun, 2009 at 08:17:08pm
Paul S - I know it isn't best suited for the 998, but its something different. I just want something different, and show it can be done.
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8604 Posts Member #: 573 Formerly Axel Podland |
15th Jun, 2009 at 08:27:32pm
On 15th Jun, 2009 1987_ParkLane said:
Paul S - I know it isn't best suited for the 998, but its something different. I just want something different, and show it can be done. I agree. One of my many enginbe projects is a supercharged 998, but using an Eaton M24 supercharger. I'm making a special pulley: 
That should give around 10psi boost on the 998 with the M24. Not much point in going much over 10psi boost on an Eaton as it starts to get inefficient IMHO. Now to slow the M45 to give 10psi boost on a 998, the pulley needs to be around 65mm dia by my calcs. Possibly too small for the belt to get a grip of the pulley and very dificult to get the crank bolt in. On 15th Jun, 2009 1987_ParkLane said:
Minimad - Yes it is due to easy, and I wish there were easier, cheaper methods out there, but there doesn't seem to be yet. It's easy to get it wrong, that's for sure. Edited by Paul S on 15th Jun, 2009. Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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22 Posts Member #: 5451 Member Melton Mowbray |
15th Jun, 2009 at 08:40:40pm
If I remember somewhere I read that the standard pully on the Eaton 45 gives around 10psi boost towards top end, I will try and find it. But I do agree, would be better with a smaller pully.
He said the piston crown was 6mm thick, and he measured the dish on a 1293 omega (6cc) and the dish was something like 5.2mm, but because the 998 pistons are a smaller diameter the dish would have to be deeper, therefore wouldn't be possible as the crown is too thin. ??
Doesn't look good :( . |
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22 Posts Member #: 5451 Member Melton Mowbray |
15th Jun, 2009 at 08:51:43pm
Also forgot to mention, they offered me the only thing they had, 998 diched Omega's...at £450 |
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8604 Posts Member #: 573 Formerly Axel Podland |
15th Jun, 2009 at 08:58:47pm
On 15th Jun, 2009 1987_ParkLane said:
If I remember somewhere I read that the standard pully on the Eaton 45 gives around 10psi boost towards top end, Right, I'm starting to feel like a miserable old git having a rant, but I am trying to guide you in the right direction. Superchargers or turbochargers do not create boost. They create an air flow that causes boost pressure. With a positive displacement supercharger, you can do some rough calcs to give an indication of likley boost. An M45 pump 45 cubic inches of air per revolution. Thats about 740cc. If you run the blower at engine speed it is pushing 1480cc into the engine. So if thats a 998, then it's taking in about 50% more air. To get the air into the engine it has to be 50% denser than normal. Thats 1.5 Bar absolute, 0.5 bar gauge or about 7.5 psig. Once you take account of the heating of the air due to the compression, then in reality that would probably be about 10 psi boost. If anyone quotes boost without reference to engine size or drive ratios, then it is of little credibilty. Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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 536 Posts Member #: 5449 Post Whore Melton Mowbray |
15th Jun, 2009 at 09:01:33pm
Would it be possible / easier to make a larger charger pulley to give the same effect of a smaller crank pulley to slow the charger down? On 25th Sep, 2009 mini13 said:
cool, i'll pop over with my tool and some lube, lol 1293 88.8hp 82.2ftlb 17.3 1/4 @ 78 mph Naturally Aspirated (for now) |
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22 Posts Member #: 5451 Member Melton Mowbray |
15th Jun, 2009 at 09:03:13pm
On 15th Jun, 2009 Paul S said:
Right, I'm starting to feel like a miserable old git having a rant, but I am trying to guide you in the right direction. Superchargers or turbochargers do not create boost. They create an air flow that causes boost pressure. With a positive displacement supercharger, you can do some rough calcs to give an indication of likley boost. An M45 pump 45 cubic inches of air per revolution. Thats about 740cc. If you run the blower at engine speed it is pushing 1480cc into the engine. So if thats a 998, then it's taking in about 50% more air. To get the air into the engine it has to be 50% denser than normal. Thats 1.5 Bar absolute, 0.5 bar gauge or about 7.5 psig. Once you take account of the heating of the air due to the compression, then in reality that would probably be about 10 psi boost. If anyone quotes boost without reference to engine size or drive ratios, then it is of little credibilty. Erm....ok 
Also the alternative, so I have been told, would be a 120thou head gasket from: http://www.performanceunlimited.co.uk/Come...istributor.html Apparantly they can order one in from the US factory, but wouldn't that be like using a decomp plate, which I'm trying to avoid? |
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22 Posts Member #: 5451 Member Melton Mowbray |
15th Jun, 2009 at 09:09:21pm
On 15th Jun, 2009 1293 sprite said:
Would it be possible / easier to make a larger charger pulley to give the same effect of a smaller crank pulley to slow the charger down? Or get one off another car or something? I imagine making one would be expensive? |
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536 Posts Member #: 5449 Post Whore Melton Mowbray |
15th Jun, 2009 at 09:14:37pm
wouldn't have thought it to be that expensive. The smaller pulleys MED do to increase boost are around £70, so shouldn't be that expensive to do a larger one? On 25th Sep, 2009 mini13 said:
cool, i'll pop over with my tool and some lube, lol 1293 88.8hp 82.2ftlb 17.3 1/4 @ 78 mph Naturally Aspirated (for now) |
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 6274 Posts Member #: 509 Post Whore Isle of Man |
15th Jun, 2009 at 09:15:11pm
dont 's have a 6cc dish as std?
"Turbo's make torque, and torque makes fun"
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22 Posts Member #: 5451 Member Melton Mowbray |
15th Jun, 2009 at 09:18:52pm
On 15th Jun, 2009 joeybaby83 said:
dont 's have a 6cc dish as std? and even forgetting that, the std 998 head is horrid by all accounts, stepping up to a 202/295 would both improve performance, and solve your cr issues I was going to get a worked head on it anyway to help lower the compression even more. |
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6274 Posts Member #: 509 Post Whore Isle of Man |
15th Jun, 2009 at 09:20:48pm
to what? "Turbo's make torque, and torque makes fun"
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22 Posts Member #: 5451 Member Melton Mowbray |
15th Jun, 2009 at 09:24:31pm
On 15th Jun, 2009 joeybaby83 said:
to what? Are we on about the same thing lol? |
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8604 Posts Member #: 573 Formerly Axel Podland |
15th Jun, 2009 at 10:12:08pm
On 15th Jun, 2009 1293 sprite said:
Would it be possible / easier to make a larger charger pulley to give the same effect of a smaller crank pulley to slow the charger down? Yes, but I could not find anything ready made suitable. Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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 9258 Posts Member #: 123 Post Whore Betwix Harrogate and York |
15th Jun, 2009 at 10:20:53pm
Just to let you know, those pistons have been in since 2007 and survived more than most 998s see. So I can comfortably say there is enough meat for a 6cc dish.
Edited by wil_h on 15th Jun, 2009. Fastest 998 mini in the world? 13.05 1/4 mile 106mph
On 2nd Jan, 2013 fastcarl said:
the design shows a distinct lack of imagination, talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry. |
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22 Posts Member #: 5451 Member Melton Mowbray |
16th Jun, 2009 at 05:29:44pm
Cheers for that wil, I will give MED a ring tomorrow about the idea you told me.
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