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WEASEL149
Joined: 19 Aug 2005 Posts: 595 Location: UK, Sheffield
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Posted: Wed Sep 16, 2015 6:16 am Post subject: |
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Raceboy wrote: | That was my guess. The rods are quite heavy and could not cope with the hugely increased tensile loads. I have never dared to rev the 924 engine past 7k on regular basis... |
It begs the question then... if you want to rev up to 7500rpm with a hotter cam in a max effort turbo engine, is it worth buying ARP bolts for stock rods, or just buying new and lighter rods with their own corresponding ARP bolts?
This is the first time my faith in the stock rods has been shaken a little.
Maybe stock rods with full prep/shot peen lightened to 815g with ARP bolts would hold up better?
It's definitely rev related failure rather than boost. It's a diesel engine so designed for high compression... _________________ 1979 UK 932 |
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DutchPug
Joined: 27 Jul 2008 Posts: 94 Location: the Netherlands
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Posted: Wed Sep 16, 2015 7:29 am Post subject: |
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Yes could very well be rpm related. But at two bar it did not hold up long, just a few hundred km and have the rev limit since i have the cam. Perhaps just a coincidence. I do intend to shift just before the limiter basically everytime i floor it, meaning i took it to 7000 - 7200 rpm a lot. It's just too much fun
Think in any case it is not sensible running high rpm with the stock rods... but if the turbo comes on boost late... you want te stretch the power-band as much as possible.
Maybe some more clues appear when taking the engine apart.
Anybody know some off the shelve forged pistons for the NA? |
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WEASEL149
Joined: 19 Aug 2005 Posts: 595 Location: UK, Sheffield
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Posted: Wed Sep 16, 2015 8:28 am Post subject: |
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Only pistons I can think of that would be almost 'off the shelf' would be Mahle VW flat tops at 87mm.
These need 22mm small end bushings or rods with 22mm small end.
Would have to check where that would leave you though with compression ratio. Can't remember off the top of my head.
Raceboy - didn't 'Racing' run 2bars with essentially a stock bottom end apart from pistons?
I think he kept stock cam though so probably didn't rev beyond 6500rpm. _________________ 1979 UK 932 |
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Raceboy
Joined: 01 Mar 2004 Posts: 2326 Location: Estonia, Europe
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Posted: Wed Sep 16, 2015 3:00 pm Post subject: |
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Jesper (Racing) did rev the engine to 7000 and occasionally to 7200 but the K27 turbo he used did not pump as much air at 2bar as Pieters Garrett and he did not use E85 _> made less power too. _________________ '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.
http://www.facebook.com/vemsporsche
Last edited by Raceboy on Wed Sep 16, 2015 6:50 pm; edited 2 times in total |
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Cedric
Joined: 27 Aug 2004 Posts: 2600 Location: Sweden
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Posted: Wed Sep 16, 2015 3:31 pm Post subject: |
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It could well be a combination of peak cylinder pressures and revs. Its easy to get extremely high pcp with E85 and high boost/aggressive timing since its not knocking. But i would have guessed the head gasket would have gone before it got to bad. But its hard to know if you cant measure it.
Stock rods are very heavy, the verdi rods that Joakim.s uses is approx almost half the weight of the stock ones. And that engine have had its fare share of beating around 7500rpm and high power figures. So it seems to work well.
BTW, great decision to continue with the 924 engine, this is one of my favorite threads! Have you logged any performance figures? 100-200 ? _________________ 1980 924 Turbo
www.instagram.com/garagecedric/ |
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morghen
Joined: 21 Jan 2005 Posts: 8868 Location: Romania
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Posted: Wed Sep 16, 2015 3:47 pm Post subject: |
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Maybe it was just a coincidence? Could it be that that rod had a fabrication defect or has had a harsh life and now you've put it up to the test?
One incident does not confirm anything IMO.
Perhaps lightened and why not stregthened stock rods would hold to 2bar and 7200RPM. Is your valve train factory? _________________ https://www.the924.com |
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Cedric
Joined: 27 Aug 2004 Posts: 2600 Location: Sweden
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Posted: Wed Sep 16, 2015 4:01 pm Post subject: |
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That is of course an important factor, could as well be just a coincidence, it could have held up for a year aswell, 1 engine is a small statistical sample
Getting lighter forged pistons+balancing of the bottom end will help aswell. Maybe shotpeen+polish the stock rods if you want to be on the safe side? _________________ 1980 924 Turbo
www.instagram.com/garagecedric/ |
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931 twinturbo
Joined: 20 Jun 2007 Posts: 122 Location: Norway
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Posted: Tue Oct 18, 2016 1:55 am Post subject: |
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Any updates? _________________ 911 Targa 1974 Turbolook/Outlaw
964 C2 1992mod
924 Carrera GTS Look(Project)
924Na stock 1982Mod
*911S Targa slantnose 1975mod
*924Na 1977Mod Carrera GT kit
*944NA Type 1 1984Mod
*924 Turbo Serie2 1980mod
*924 Turbo Serie2 1980Mod
*924NA 1982Mod |
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mikeycrum14
Joined: 19 Jan 2017 Posts: 110 Location: Juneau, Wisconsin
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Posted: Fri Feb 03, 2017 8:08 am Post subject: Total Newbie |
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Looking for performance upgrades on my NA 924. the engine is bone stock. five speed trans and a Stage 3 racing clutch (apparently). Looking to upgrade the engine cheaply and safely without ruining reliability. Ive heard about upgrading to EFI from the CIS. What would that entail? any suggestions on upgrades. minimal car knowledge (first car). _________________ 1981 924 - Alpine White, First car! LSD. - SOLD
1989 Foxbody - Oxford White Turd
1992 Miata - Freaking Red
1987 300zx Turbo - Also White
1991 Miata - White field find
1987 924S - Alpine White, Offroader Build, possible future TDI swap |
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DutchPug
Joined: 27 Jul 2008 Posts: 94 Location: the Netherlands
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Posted: Sat Mar 04, 2017 8:43 pm Post subject: |
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Update...; No time for this car. Have not even touched it since.
Have a spare engine and ordered billet connecting rods 4 months back, should be here soon. Still looking for pistons.
The idea is to make a stronger engine and upgrade both the intake and exhaust manifolds. But, don't hold your breath on updates |
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safe
Joined: 18 Mar 2017 Posts: 583 Location: Sweden
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Posted: Mon Oct 31, 2022 6:11 pm Post subject: |
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DutchPug wrote: |
Have tuned the engine as it is on E85... unfortunately at 1 bar some fuel supply issues --> am going to install a larger pump now.
Perhaps interesting to hear, at just 1.0 bar boost pressure the engine already made 248 whp... (compared to 229 at 1.2 bar with normal fuel).
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No new engine yet?
I read this tread a couple of years ago and got inspired. Figured I would go with stronger rods right away, but it hasen't happened yet...
But the original stock (mostly) engine is now boosted to 1.0 bar. Made 235 whp and 330Nm, which is near your power figures. This is where my uprated clutch is limiting me.
Pretty cool these engines can make this power on stock components with a head that flows as badly as it does. _________________ /Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe |
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Cedric
Joined: 27 Aug 2004 Posts: 2600 Location: Sweden
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Posted: Mon Oct 31, 2022 7:57 pm Post subject: |
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safe wrote: | DutchPug wrote: |
Have tuned the engine as it is on E85... unfortunately at 1 bar some fuel supply issues --> am going to install a larger pump now.
Perhaps interesting to hear, at just 1.0 bar boost pressure the engine already made 248 whp... (compared to 229 at 1.2 bar with normal fuel).
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No new engine yet?
I read this tread a couple of years ago and got inspired. Figured I would go with stronger rods right away, but it hasen't happened yet...
But the original stock (mostly) engine is now boosted to 1.0 bar. Made 235 whp and 330Nm, which is near your power figures. This is where my uprated clutch is limiting me.
Pretty cool these engines can make this power on stock components with a head that flows as badly as it does. |
This was really a great thread, but since DutchPug seems to have stopped working on the car you have inherited the roll Now its your turn to see how far the ol n/a can be pushed. _________________ 1980 924 Turbo
www.instagram.com/garagecedric/ |
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safe
Joined: 18 Mar 2017 Posts: 583 Location: Sweden
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Posted: Mon Oct 31, 2022 8:19 pm Post subject: |
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Cedric wrote: | safe wrote: | DutchPug wrote: |
Have tuned the engine as it is on E85... unfortunately at 1 bar some fuel supply issues --> am going to install a larger pump now.
Perhaps interesting to hear, at just 1.0 bar boost pressure the engine already made 248 whp... (compared to 229 at 1.2 bar with normal fuel).
|
No new engine yet?
I read this tread a couple of years ago and got inspired. Figured I would go with stronger rods right away, but it hasen't happened yet...
But the original stock (mostly) engine is now boosted to 1.0 bar. Made 235 whp and 330Nm, which is near your power figures. This is where my uprated clutch is limiting me.
Pretty cool these engines can make this power on stock components with a head that flows as badly as it does. |
This was really a great thread, but since DutchPug seems to have stopped working on the car you have inherited the roll Now its your turn to see how far the ol n/a can be pushed. |
Will do when funds for a new clutch is availible! Then on to new rods and maxing out the turbo.
I'm moving my storage to a new location and has found stuff I don't need and might be able to sell.
Yesterday I also found a cracked wheel barrel on the 911 that need be replaced and that takes priority. _________________ /Magnus, Stockholm Sweden
=======================
Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe |
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