Notices
Engine Performance This section is for discussion on all engine building related questions.
Sponsored by:
Sponsored by: KPower

7800rpm might be too much for the mighty K24z3

Old Apr 10, 2026 | 05:20 PM
  #61  
rabid's Avatar
Thread Starter
Junior Member
 
Joined: Dec 2019
Posts: 103
Total Cats: 13
Default

This was another salvage yard engine just like the first one. This one was probably in better condition than the first one too judging by the better compression numbers. Hard to say though. I beat on this engine all winter on the back roads messing with my boost control and stuff. I kept the boost a little lower than the first one too. It saw like 4 days of autocross with a little rev limiter here and there. It died on run 4 Saturday.
Old Apr 11, 2026 | 11:33 AM
  #62  
curly's Avatar
Cpt. Slow
iTrader: (25)
 
Joined: Oct 2005
Posts: 15,192
Total Cats: 1,398
From: Oregon City, OR
Default

Rods breaking like that have usually experienced an over-rev. I log RPMs at the highest frequency possible, even a brief downshift a little early can weaken an engine. Not saying you did it, if it was out of a manual car, could've been the previous owner.
Old Apr 11, 2026 | 12:47 PM
  #63  
rabid's Avatar
Thread Starter
Junior Member
 
Joined: Dec 2019
Posts: 103
Total Cats: 13
Default

Originally Posted by curly
Rods breaking like that have usually experienced an over-rev. I log RPMs at the highest frequency possible, even a brief downshift a little early can weaken an engine. Not saying you did it, if it was out of a manual car, could've been the previous owner.
Not sure I ever did but possible. It was out of an automatic. I have never found one out of a manual yet. Which is an interesting point. Auto cars are probably less abused because it's not really possible to. I log at 5ms rate. Here is a screenshot.


My plan is to get this engine in, put it on a dyno to see what it is actually doing, lower the rev limiter a little, building a new bottom end, swap it when I can.
Old Apr 16, 2026 | 05:57 PM
  #64  
rabid's Avatar
Thread Starter
Junior Member
 
Joined: Dec 2019
Posts: 103
Total Cats: 13
Default

New engine is in. It doesn't know about those that have fallen before it. I set the hard limit 7000. Turned off progressive cylinder shutoff. So spark retard and then spark/fuel cut at limit.
I need to investigate flat shift. It seems like the engine overshoots quite a bit when the clutch is pressed. I need to log this and see what's going on.
Old Apr 21, 2026 | 07:03 PM
  #65  
rabid's Avatar
Thread Starter
Junior Member
 
Joined: Dec 2019
Posts: 103
Total Cats: 13
Default

It is crazy how the rpm jumps 700 rpm with flat shift. The clutch release and rpm climbs. The switch activates and 40ms the fuel shuts off. I assume the spark is cut off too. But the rpms still climb. Is boost driving the pistons to higher speed?
It is crazy how the rpm jumps 700 rpm with flat shift. The clutch release and rpm climbs. The switch activates and 40ms the fuel shuts off. I assume the spark is cut off too. But the rpms still climb. Is boost driving the pistons to higher speed?
Old Apr 21, 2026 | 10:26 PM
  #66  
thebeerbaron's Avatar
Senior Member
iTrader: (1)
 
Joined: Dec 2007
Posts: 1,036
Total Cats: 495
From: San Jose
Default

I know very little about flat shift, but does your clutch switch activate at the top or bottom of the stroke? The stock one activates at the top, when you first start to move the pedal.
Old Apr 21, 2026 | 11:04 PM
  #67  
SimBa's Avatar
Elite Member
iTrader: (1)
 
Joined: Oct 2022
Posts: 1,820
Total Cats: 285
From: Idaho
Default

I would double check that spark is being cut. I just checked back on a log of my flat shifting and it looks like it's doing a full ignition cut. I think I tried fuel cut but it might've been too slow like what you're seeing.


Old Apr 21, 2026 | 11:24 PM
  #68  
rabid's Avatar
Thread Starter
Junior Member
 
Joined: Dec 2019
Posts: 103
Total Cats: 13
Default

Top
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
pdexta
Dynos and timesheets
98
Jul 28, 2024 05:29 PM
Godless Commie
Engine Performance
5
Mar 28, 2021 07:25 PM
AndrewG
ECUs and Tuning
5
Oct 15, 2018 04:07 PM
xXxKillDogxXx
Build Threads
29
Nov 13, 2015 01:17 AM
N3v
MEGAsquirt
9
May 13, 2009 11:43 AM


Thread Tools
Search this Thread

All times are GMT -4. The time now is 06:35 PM.