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simsport
Joined: 06 Nov 2002
Posts: 573
Location: UK Warrington
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 Posted: Sun Aug 05, 2012 10:13 pm Post subject: All gone wrong! |
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Well after nealry a full year not running due to hard to find elec fault (MOTEC ecu appears to fail under load, circuit board fault possibly) I got the car out at Goodwood.
Ironic really as its the track in the Board top picture (Graham Rose overturning at the chicane) Anyway the car was doing well on the back straight, pulling around 5500 in 5th so approx 130mph with the 944s2 box, when water and steam blew out the back edge of the bonnet and in the space of a few seconds she ran very rough.
I coasted in to find that the water header tank (original 924) had punched a hole in the small recess you can see on the top side of it, just to the left of the filler cap, and blonw a column of hot water out, this will have emptied the system in seconds and then the head gasket went in sympathy!
(Anyone had a tank fail before?)
I suppose it could be said the gasket failed and allowed the tank to pressurise but, the head has sealed well for years on a std gasket and the boost level was no more than one bar, I suspect the tank but either way its all toast, so rebuild on the way this winter.
Will need pistons , rods , bearings etc plus better head gasket and may go for the lighter valve gear.
Cheers
Simon
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morghen
Joined: 21 Jan 2005
Posts: 9095
Location: Romania
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| Posted: Mon Aug 06, 2012 12:22 am Post subject: |
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i'm puting my money on the following scenario:
head gasket developed a slight leak that got larger and larger until it pumped serious pressure into the water tank. The water tank blew.
thats exactly what happend to me. the tank cracked right near the filler cap.
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924RACR
Joined: 29 Jul 2001
Posts: 9070
Location: Royal Oak, MI, USA
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| Posted: Mon Aug 06, 2012 2:21 am Post subject: |
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Wow! Yeah, I've had old header tanks fail, sadly. Had to replace the one on my 931. Though the failure wasn't quite as spectacular... 
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'79 924 #77 SCCA H Prod racecar
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Raceboy
Joined: 01 Mar 2004
Posts: 2327
Location: Estonia, Europe
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| Posted: Mon Aug 06, 2012 4:23 pm Post subject: |
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Sorry to hear about the failure Simon.
But my bet would be blown head gasket -> ruptured tank not vice versa. Head gasket deteriorates with age and they blow even with stock engines that doesn't see any boost.
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'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold 
'84 924, turbocharged, sold.
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leadfoot
Joined: 11 Dec 2002
Posts: 2222
Location: gOLD cOAST Australia
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| Posted: Tue Aug 07, 2012 6:15 pm Post subject: |
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bummer Simon,
I suppose a new build thread is in order then...
how was the motec treating you till then?? I'm considering EFI again and would be interested in the haltec/mptec comparison...
even thinking of a basic microtec system considering its also local...
Stu
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simsport
Joined: 06 Nov 2002
Posts: 573
Location: UK Warrington
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| Posted: Mon Aug 13, 2012 9:20 am Post subject: Motec |
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Hi Stu
The motec was good, power and torque was better with it than the previous system I think in part due to the number of mapping points which are greater with the Motec than the old system.
Took the blower and intake side off the engine, water in the supercharger and intake manifold!...not good 
Cheers
Simon
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Raceboy
Joined: 01 Mar 2004
Posts: 2327
Location: Estonia, Europe
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| Posted: Mon Aug 13, 2012 4:10 pm Post subject: Re: Motec |
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| simsport wrote: | Hi Stu
The motec was good, power and torque was better with it than the previous system I think in part due to the number of mapping points which are greater with the Motec than the old system.
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It is more to do with the CPU and fuel+ign table calculating algorithm as these factors determine the ECU's ability to interpolate between cells.
Autronic (and VEMS also) for example can run the engine even on 2x2 tables without big problems. I think there are many ECU's that can do that also.
My bet would be on better tuner + the placebo effect unless you have direct comparisons on the dyno.
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'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
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simsport
Joined: 06 Nov 2002
Posts: 573
Location: UK Warrington
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| Posted: Tue Aug 14, 2012 8:19 am Post subject: Placebo |
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Well I do take your point but after 20 years of competing with the car I reckon I can tell if its real or not, but I do recognise how even a change in noise can fool you into thinking its somehow better than before. Its a bit like the events themselves, sometimes you think a timed lap is quicker only to find that you being busy behind the wheel was actualy slower overall.
I can say with confidence that the car made about 20 bhp just by fitting the motec system. It was mapped on the same rollers by the same experienced guy and the only things we could see that were very different were the sequential injection and the MOTEC system. The previous sytem was good but basic with none of the expansion possibilities of the MOTEC.
A choice of system is always going to be influenced by numerous things. Sometimes its due to cost constraints or you have good feedback from other users and another time its due to somebody local knowing the system and being a supplier/tuner. It was this last reason that swung it for me .
It was fine with the earlier system for a long time but when I had a problem and I asked for a software update my older model of ECU/system had been dropped. I could understand why, it was an early model , but it shook my confidence in that make. With MOTEC the system is supported (I think for life) and its software is updated. Add that to the fact I have a local expert (and good friend) who installs them and it was a no brainer really.
Cheers
Simon
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Raceboy
Joined: 01 Mar 2004
Posts: 2327
Location: Estonia, Europe
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| Posted: Tue Aug 14, 2012 5:04 pm Post subject: Re: Placebo |
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| simsport wrote: | ...and another time its due to somebody local knowing the system and being a supplier/tuner. It was this last reason that swung it for me .
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This should always be the main reason to choose or not to choose a standalone unless one could and want to DIY the install and tune.
My experience (with numerous standalones, including Autronic, Motec, Tatech, VEMS, MS, KMS etc) shows that usually if maximum power is much different then something is wrong with timing calculations (one ecu cannot calculate timing precisely enough for example, google for timing drift).
Difference comes from what's under the curve: transient response, compensation tables, boost control etc and how good these things work.
I find Motec to be a good but expensive system (you have to pay even for logging capability) with somewhat dated inerface. But to each their own and if I would have to choose some higher end ECU it would be Pectel SQ6 or the like (bass GT bought one for his project, wonder what he is doing now?).
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'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
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morghen
Joined: 21 Jan 2005
Posts: 9095
Location: Romania
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| Posted: Tue Aug 14, 2012 6:36 pm Post subject: Re: Placebo |
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| Raceboy wrote: | | If I would have to choose some higher end ECU it would be Pectel SQ6 or the like (bass GT bought one for his project, wonder what he is doing now?). |
OT:
He's goone missing, i've wrote him a few times but i got nothing back.
I hope he's ok.
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simsport
Joined: 06 Nov 2002
Posts: 573
Location: UK Warrington
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| Posted: Wed Aug 15, 2012 4:13 am Post subject: bass gt |
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I dont know, I have tried to find him via email etc but no joy, He always got back to us in the past. He was living/working abroad so he may just have changed his email details.
Cheers
Simon
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ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
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| Posted: Wed Aug 15, 2012 4:44 am Post subject: |
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Last I corresponded with Steve he was in South Africa on a major project and had no time for cars...haven't heard from him in at least two years...
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erstwhile owner of just about every 924 variant ever made |
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morghen
Joined: 21 Jan 2005
Posts: 9095
Location: Romania
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| Posted: Wed Aug 15, 2012 5:08 am Post subject: |
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he is not responding via email, i just called his old cell phone number, it rang but nobody answered, i left a message.
i'll keep calling.
Simon, too bad for the engine, but if it held nicely for years i think it did its job. Time for a nice rebuild thread
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