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PostPosted: 05 Dec 2015 10:37 
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Joined: 30 Nov 2015 09:24
Posts: 21
Country: Malaysia
Hi guys, I'm new here and can't really find much info on this.

I just blew my stock but built engine on my Proton Waja and had sourced a 4g92 MIVEC engine and am currently planning to rebuild it with a 4g93 GSR block, 4agze pistons and CA18 conrods and also running on a Megasquirt MS3X Standalone management system tuned by myself.

I'm just wondering, the stock 4g92 MIVEC engine had a rev limit of 8200rpm with 81.0 x 77.5 bore and stroke but with the 4g93 crankshaft increasing the stroke by so much and also the extra weight of the CA18 conrods, what rev limits should I set to keep myself safe?

Determining the engine's revcut at this point is kinda important to me as it also determines the size of the turbo i'd be putting on it and also whether if I'd have to change the MIVEC short final drive ratio with a longer one.

Thanks a bunch guys!


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PostPosted: 07 Dec 2015 15:54 
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Joined: 27 Oct 2013 00:56
Posts: 48
Country: australia
mine revs to 7K rpm which is around 500 short of factory redline on the tach on a gsr (the 7k is where it makes peak power revs out to 7500.) if your tuning it run it and find out where it makes peak then go a few hundred over that for limiter.

it could probably go higher but piston speeds and the forces involved would increase significantly,


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PostPosted: 09 Dec 2015 21:37 
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Joined: 15 Feb 2011 08:51
Posts: 890
Country: Australia
No one would be able to answer that with any degree of accuracy.

If it was to stay NA and use OEM 4G93 rods etc, I've read some people rev to 8,000rpm without any problems.

But non OEM internals coupled with boost makes it a guessing game.

You can compare the 4AGZE and CA18 R/S ratio, and stroke and have some idea of rev limit I guess (ie, if the R/S is better, and stroke shorter in the 4G93 compared to those engines, then it should be safe to rev to at least those engine's cutout rpm)


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PostPosted: 09 Dec 2015 21:59 
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Joined: 04 Jul 2005 13:25
Posts: 1205
Location: Lower Hutt
Country: NZ
It's a bit like asking how much power an engine can make on stock internals.

Hardly anyone can answer that because most breakages are due to bad tuning.

All parts have limits.
When it comes to stock conrods, I don't think I've ever seen one fail because it wasn't strong enough.
I've seen plenty of cylinder blocks with holes in the side because the rod broke.
The big end bolts can and DO fail on some engines.........that's NOT the conrod. More revs put more stress on the bolts. Boost will put more stress on the rods, not the bolts.
The nuts can come undone because they weren't tightened properly. That's not the fault of the conrod either.
I've broken a conrod myself. Piston to bore (forged piston) clearance wasn't enough for the loading and tune on the engine. That wasn't the fault of the conrod either. The pistons get stuck and the crank pulls on the conrod which pulls the gudgeon pin out of the bottom of the piston, snaps the top off the conrod when one side of the piston lets go.

My own engine in the car right now, stock rods, stock bolts, ........well, completely factory engine.......stroke is 76mm, stock red line about 7200, I've had it out to 8500 a few times. It'll do it a few more times too. Long term, it's bound to break, everything does.
To me, good knock free tuning is more important than aftermarket up/downgraded parts.
Stronger rod bolts might be an idea IF and only IF aftermarket ones are stronger than stock?
How would you actually know?

How far do you need to rev it?
IN N/A form, so long as the torque stays flat, like they do from the factory, the power will keep going up with revs.
Add a turbo, so long as the boost doesn't drop off too much with higher revs, the power will keep going up too.
Non mivec turbo engines, often they'll make peak power at 5500 or a bit more RPMs so there's not much point in going over 7000.


Nightstalker1993 wrote:

I just blew my stock but built engine on my Proton Waja and had sourced



If you can figure out what went wrong....make sure it doesn't happen again?

_________________
6G72 mivec Twin TDO5 20Gs up and running.
Scrapheap special making exactly 280 horses at some unknown rpm.
Engine dyno under construction.

It's easier to fool someone than it is to convince someone that they've been fooled.


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PostPosted: 10 Dec 2015 22:38 
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Joined: 27 Oct 2013 00:56
Posts: 48
Country: australia
Ive seen an na one bend factory rods. But it was a raced engine beong pushed right to the limit the b18 has a beter rod stroke than the 93. Does


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PostPosted: 04 Aug 2016 03:45 
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Joined: 30 Nov 2015 09:24
Posts: 21
Country: Malaysia
leadfoot wrote:
mine revs to 7K rpm which is around 500 short of factory redline on the tach on a gsr (the 7k is where it makes peak power revs out to 7500.) if your tuning it run it and find out where it makes peak then go a few hundred over that for limiter.

it could probably go higher but piston speeds and the forces involved would increase significantly,


I'm expecting 7500-8000rpm as a limit. Chose a TD05 twin scroll turbo off an Evo 6 which is pretty modern and an efficient design which should give quick spool up and early boost for a 1.8.


Spetz wrote:
No one would be able to answer that with any degree of accuracy.

If it was to stay NA and use OEM 4G93 rods etc, I've read some people rev to 8,000rpm without any problems.

But non OEM internals coupled with boost makes it a guessing game.

You can compare the 4AGZE and CA18 R/S ratio, and stroke and have some idea of rev limit I guess (ie, if the R/S is better, and stroke shorter in the 4G93 compared to those engines, then it should be safe to rev to at least those engine's cutout rpm)


One of my friend who works in the automotive industry just ask me to calculate the mean piston speed and find out at what RPM is the speed equivalent on the 4g93 with the 4g92 at redline. According to the calculation, a 4g93 at 7140rpm would have the same mean piston speed as a 4g92 at 8200rpm so I guess that answers my initial question. And to your statement, running a 4g93 at 8000rpm would give the same mean piston speed as a 4g92 at 9200rpm. That's a hell lot of stress!

Anyway, I went with a set of forged H beam conrods so it should handle the stresses much better.

magn1t wrote:
It's a bit like asking how much power an engine can make on stock internals.

Hardly anyone can answer that because most breakages are due to bad tuning.

All parts have limits.
When it comes to stock conrods, I don't think I've ever seen one fail because it wasn't strong enough.
I've seen plenty of cylinder blocks with holes in the side because the rod broke.
The big end bolts can and DO fail on some engines.........that's NOT the conrod. More revs put more stress on the bolts. Boost will put more stress on the rods, not the bolts.
The nuts can come undone because they weren't tightened properly. That's not the fault of the conrod either.
I've broken a conrod myself. Piston to bore (forged piston) clearance wasn't enough for the loading and tune on the engine. That wasn't the fault of the conrod either. The pistons get stuck and the crank pulls on the conrod which pulls the gudgeon pin out of the bottom of the piston, snaps the top off the conrod when one side of the piston lets go.

My own engine in the car right now, stock rods, stock bolts, ........well, completely factory engine.......stroke is 76mm, stock red line about 7200, I've had it out to 8500 a few times. It'll do it a few more times too. Long term, it's bound to break, everything does.
To me, good knock free tuning is more important than aftermarket up/downgraded parts.
Stronger rod bolts might be an idea IF and only IF aftermarket ones are stronger than stock?
How would you actually know?

How far do you need to rev it?
IN N/A form, so long as the torque stays flat, like they do from the factory, the power will keep going up with revs.
Add a turbo, so long as the boost doesn't drop off too much with higher revs, the power will keep going up too.
Non mivec turbo engines, often they'll make peak power at 5500 or a bit more RPMs so there's not much point in going over 7000.


Nightstalker1993 wrote:

I just blew my stock but built engine on my Proton Waja and had sourced



If you can figure out what went wrong....make sure it doesn't happen again?


More revs put more stresses on the bolt, but also more stresses on the conrod as well in terms of tension, but more boost only increases the compression force of the piston slightly, when compared to the relation of rpm x stress compared to boost x stress.

The way my engine blew is quite peculiar. My ECU(Megasquirt MS3x) have a pitlane limiter feature which can also be used as a rolling launch control. Hit the rolling launch control at 2nd gear and floored the throttle at 5000rpm which the ECU holds and the engine builds up to 1.3bar of boost. 3 seconds after I hit the switch, conrod #1 decided to leave the engine. Before that, the engine survived a circuit track session in Sepang with no issues, 1.2bar boost and 7000rpm with no problem, but it blew up at 5000rpm and 1.3bar boost when it was holding revs. I suspect at that certain RPM and boost level the rotating assembly may had hit a resonance frequency or something or could be just failure of the rod bolts. The engine was a 4g18 engine running forged rods and turbo pistons, the rod smashed 2 large holes on the block and was nowhere to be found while pistons shattered into a million pieces in the sump.

leadfoot wrote:
Ive seen an na one bend factory rods. But it was a raced engine beong pushed right to the limit the b18 has a beter rod stroke than the 93. Does


True, calculating the rod stroke ratio of the 92 or 93, it's pretty sad actually

Sorry for the 8 months delayed reply :lol: . My engine is still being built though, would be posting details in the member's ride section soon


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