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Power thru 'special' upper cam shaft timing gear.
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newbie924  



Joined: 16 Mar 2016
Posts: 75
Location: EUROPE MALTA

PostPosted: Thu Nov 29, 2018 10:20 pm    Post subject: Reply with quote

safe wrote:
nickthompson wrote:
The stock compression at it's highest in a 924 is 9.3:1. I'd say that's pretty boostable. The 1.8t VW/AUDI has 9.2:1 and people run 16 PSI boost in those engines.


I agree!
I have an NA engine that's going to be boosted, if I can find some usable pistons or a solution for worn ring grooves...
Worst case (which is only worst for the wallet) I buy new JEs, but then it will be delayed for other projects.

I think that a reduction to 9:1 would be good, but that is achievable with a thicker head gasket.


So from a certain point of view as you say if you turbo the engine , compression from 'cylinder head' mods can be achieved or decreased. I would think therefore that the thicker the head gasket , more (not exaggerated) boost can be applied?
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safe  



Joined: 18 Mar 2017
Posts: 21
Location: Sweden

PostPosted: Thu Nov 29, 2018 10:58 pm    Post subject: Reply with quote

Yes, I think so.
With slightly thicker MLS gasket, better headstuds (because if the head lifts the gasket goes), and controlling the temperature 1 bar of boost would be reliable on gasoline. With E85 a lot more, that's what I'm aiming for anyway.

My recipe would be:
-Thicker MLS headgasket (if using stock pistons)
-ARP headstuds
-Stronger/lighter rods
-Lightly ported head
-E85
-EFI, with wideband lambda och preferably egt sensors.
-Intercooler, front mounted with good flow.
-oil cooler

Further, the clutch would need an upgrade....

Edit:
A powerful spark is important too for reliable combustion, haven't researched any alternatives yet.
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CÚdric  



Joined: 27 Aug 2004
Posts: 1766
Location: Sweden

PostPosted: Fri Nov 30, 2018 1:53 am    Post subject: Reply with quote

safe wrote:
Yes, I think so.
With slightly thicker MLS gasket, better headstuds (because if the head lifts the gasket goes), and controlling the temperature 1 bar of boost would be reliable on gasoline. With E85 a lot more, that's what I'm aiming for anyway.

My recipe would be:
-Thicker MLS headgasket (if using stock pistons)
-ARP headstuds
-Stronger/lighter rods
-Lightly ported head
-E85
-EFI, with wideband lambda och preferably egt sensors.
-Intercooler, front mounted with good flow.
-oil cooler

Further, the clutch would need an upgrade....

Edit:
A powerful spark is important too for reliable combustion, haven't researched any alternatives yet.


That will give you a very nice engine, if it is combined with a high efficiency charger like a fairly modern TD04 /05 or similar. Lighter rods would be nice for higher engine speeds, but they will probably be just fine for std rev limit. They are crazy heavy though compared to high end forged rods.
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newbie924  



Joined: 16 Mar 2016
Posts: 75
Location: EUROPE MALTA

PostPosted: Fri Nov 30, 2018 7:12 am    Post subject: Reply with quote

Speaking of spark, my 924 has a factory fitted electronic ignition system, the car is a 1981 model, so its not a early type, could anything else better this unit, or shall I stick to it? Anyone??? BTW Cedric my tuner told me that the longer velocity stacks which I call trumpets which I havestored in a cupboard in my garage would help to give out more torque in low revs, and since the events I wish to take part in are short hill climbs and short circuits I think the longer stacks would be the best choice for this little race car Im trying to put together, could I be wrong here? https://www.youtube.com/watch?v=7xmNEESXbmc
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CÚdric  



Joined: 27 Aug 2004
Posts: 1766
Location: Sweden

PostPosted: Fri Nov 30, 2018 8:38 am    Post subject: Reply with quote

newbie924 wrote:
Speaking of spark, my 924 has a factory fitted electronic ignition system, the car is a 1981 model, so its not a early type, could anything else better this unit, or shall I stick to it? Anyone??? BTW Cedric my tuner told me that the longer velocity stacks which I call trumpets which I havestored in a cupboard in my garage would help to give out more torque in low revs, and since the events I wish to take part in are short hill climbs and short circuits I think the longer stacks would be the best choice for this little race car Im trying to put together, could I be wrong here? https://www.youtube.com/watch?v=7xmNEESXbmc


Yes, longer will move the powerband down, try them both if you are curious. How long is the intake now?
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nickthompson  



Joined: 26 Mar 2013
Posts: 863
Location: Central Georgia

PostPosted: Fri Nov 30, 2018 11:10 am    Post subject: Reply with quote

newbie924 wrote:
Speaking of spark, my 924 has a factory fitted electronic ignition system, the car is a 1981 model, so its not a early type, could anything else better this unit, or shall I stick to it?


I've run MSD ignition before but my factory unit crapped out. I wouldn't replace it if it works.
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newbie924  



Joined: 16 Mar 2016
Posts: 75
Location: EUROPE MALTA

PostPosted: Fri Nov 30, 2018 10:05 pm    Post subject: Reply with quote

CÚdric wrote:
newbie924 wrote:
Speaking of spark, my 924 has a factory fitted electronic ignition system, the car is a 1981 model, so its not a early type, could anything else better this unit, or shall I stick to it? Anyone??? BTW Cedric my tuner told me that the longer velocity stacks which I call trumpets which I havestored in a cupboard in my garage would help to give out more torque in low revs, and since the events I wish to take part in are short hill climbs and short circuits I think the longer stacks would be the best choice for this little race car Im trying to put together, could I be wrong here? https://www.youtube.com/watch?v=7xmNEESXbmc


Yes, longer will move the powerband down, try them both if you are curious. How long is the intake now?


I will take measurements tomorrow as I only do some work on the car on a Saturday and sometimes when its raining or very cold on a Sunday too, but dont worry I will let you know.
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newbie924  



Joined: 16 Mar 2016
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Location: EUROPE MALTA

PostPosted: Fri Nov 30, 2018 10:06 pm    Post subject: Reply with quote

nickthompson wrote:
newbie924 wrote:
Speaking of spark, my 924 has a factory fitted electronic ignition system, the car is a 1981 model, so its not a early type, could anything else better this unit, or shall I stick to it?


I've run MSD ignition before but my factory unit crapped out. I wouldn't replace it if it works.


Seems to work fine, any reason for not changing it my friend?
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newbie924  



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PostPosted: Sun Dec 02, 2018 4:20 am    Post subject: Reply with quote

Hello Cedric. the inlet manifold measures 3inches, the webers measure another 4 and half inches.. The velocity stacks which are fitted on the car right now measure 2 inches, total of 9 & half inches. I have 2 other sets of velocity stacks which I call trumpets, these are 2 & half inches and 3 inches. Due o the shortness of our events here measuring from chicane to chicane in a hillclimb for example I would think that the longer ones would be the best fit for my requirements.
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CÚdric  



Joined: 27 Aug 2004
Posts: 1766
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PostPosted: Sun Dec 02, 2018 5:34 am    Post subject: Reply with quote

That is about 240mm, significantly shorter Tha the std intake, even if you add 50mm it will still be shorter than the original. I don't remember the std numbers, but 350mm somewhere if I remember correctly. It will definitely move the powerband upwards, wish I had access to my engine simulation model, that would show how it affects the powerband. You can make some rough calculations though to match the length for a certain desired rpm.
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Raceboy  



Joined: 01 Mar 2004
Posts: 2305
Location: Estonia, Europe

PostPosted: Mon Dec 03, 2018 5:08 pm    Post subject: Reply with quote

Fifty50Plus wrote:
The bottom end of the NA and Turbo are identical internally and strong like bull. Same block, same crank, same rods, same bearings. Pistons and head are different for the turbo version. If you want to boost an NA, you must at least change the pistons to a lower compression ratio over stock.
The turbo pan has an extra hole for oil return from the cooler.


There's no need to lower compression ratio on 924 engine. Head flows badly and you can safely run 1bar and even more with totally reasonable ignition advance. Me and Pieter (Dutchpug) have done it and iirc he pushed his euro 924 stock engine up to 352 rwhp on E85.
I got 237 rwhp with pump gas (98 octane here, 93 in US) at 1.1 bar back in the day, the same engine still runs strong in my friends car 11 years after boosting it.
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morghen  



Joined: 21 Jan 2005
Posts: 7910
Location: Romania

PostPosted: Mon Dec 03, 2018 6:49 pm    Post subject: Reply with quote

Raceboy wrote:
the same engine still runs strong in my friends car 11 years after boosting it.


Jesus, time flies..seems like yesterday.
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CÚdric  



Joined: 27 Aug 2004
Posts: 1766
Location: Sweden

PostPosted: Mon Dec 03, 2018 9:19 pm    Post subject: Reply with quote

Raceboy wrote:
Fifty50Plus wrote:
The bottom end of the NA and Turbo are identical internally and strong like bull. Same block, same crank, same rods, same bearings. Pistons and head are different for the turbo version. If you want to boost an NA, you must at least change the pistons to a lower compression ratio over stock.
The turbo pan has an extra hole for oil return from the cooler.


There's no need to lower compression ratio on 924 engine. Head flows badly and you can safely run 1bar and even more with totally reasonable ignition advance. Me and Pieter (Dutchpug) have done it and iirc he pushed his euro 924 stock engine up to 352 rwhp on E85.
I got 237 rwhp with pump gas (98 octane here, 93 in US) at 1.1 bar back in the day, the same engine still runs strong in my friends car 11 years after boosting it.


One thing people often dont think about is the flow motion in the cylinder. An inlet channel like the N/A will get flow separation at the inner radius, which in turn will create alot of flow motion in the cylinder, the drawback is of course low flow numbers. But high flow motion have a significant impact on knock probability in the cumbustion chamber, and can make the combustion more resitant to detonation than a higher flowing port.

The development of the in cylinder flow is one significant reason to why modern engines can run much higher CR than old ones, without detonation. (of course there are many more). Of course we have 2v heads which creates a swirling motion aswell, which isnt as effective for knock reduction, modern 4v designs are often better.

If you look at a modern intake port they look very weird, not at all like a "ported high flow port", they are designed to have flow separation at the inner radius to create a tumbling motion in the cylinder. Heres a pic from VW EA288 and EA288EVO (more tumble)


sooo, alot of info, but can be a reason why the trusty old n/a engine can take boost very well.
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safe  



Joined: 18 Mar 2017
Posts: 21
Location: Sweden

PostPosted: Mon Dec 03, 2018 10:07 pm    Post subject: Reply with quote

CÚdric wrote:
Raceboy wrote:
Fifty50Plus wrote:
The bottom end of the NA and Turbo are identical internally and strong like bull. Same block, same crank, same rods, same bearings. Pistons and head are different for the turbo version. If you want to boost an NA, you must at least change the pistons to a lower compression ratio over stock.
The turbo pan has an extra hole for oil return from the cooler.


There's no need to lower compression ratio on 924 engine. Head flows badly and you can safely run 1bar and even more with totally reasonable ignition advance. Me and Pieter (Dutchpug) have done it and iirc he pushed his euro 924 stock engine up to 352 rwhp on E85.
I got 237 rwhp with pump gas (98 octane here, 93 in US) at 1.1 bar back in the day, the same engine still runs strong in my friends car 11 years after boosting it.


One thing people often dont think about is the flow motion in the cylinder. An inlet channel like the N/A will get flow separation at the inner radius, which in turn will create alot of flow motion in the cylinder, the drawback is of course low flow numbers. But high flow motion have a significant impact on knock probability in the cumbustion chamber, and can make the combustion more resitant to detonation than a higher flowing port.

The development of the in cylinder flow is one significant reason to why modern engines can run much higher CR than old ones, without detonation. (of course there are many more). Of course we have 2v heads which creates a swirling motion aswell, which isnt as effective for knock reduction, modern 4v designs are often better.

If you look at a modern intake port they look very weird, not at all like a "ported high flow port", they are designed to have flow separation at the inner radius to create a tumbling motion in the cylinder. Heres a pic from VW EA288 and EA288EVO (more tumble)


sooo, alot of info, but can be a reason why the trusty old n/a engine can take boost very well.


They should have put the NA head on the turbo and the turbo head on the NA !
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newbie924  



Joined: 16 Mar 2016
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PostPosted: Mon Dec 03, 2018 11:00 pm    Post subject: Reply with quote

Would the turbo head fit without any problems on the NA block since the blocks are the same? Also can COP's be fitted to a webered engine, or does this require any major mods... I think that the COP system would more suit a turbo head since the plugs are on the inlet side and therefore will not be effected by exhaust heat. These thoughts would all be for future modsbut good to know as Im quite happy with the car as is for now mechanically since I still have body work/paint to do.
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