6m v.s. 7m crank
- Thread starter terror
- Start date
6M more responsive but harsher
7M less responsive but smoother across the entire range.
Yes interchangable.
7M less responsive but smoother across the entire range.
Yes interchangable.
IJ, can you (or another expert, I suppose) tell me why the 7M crank, which is smoother, has a lower redline? It seems counter-intuitive that the harsher crank has the higher redline. :dunno:
My half-educated guess is that the added weight on the 7M would put more stress on bearings at higher engine speeds, but if it is properly balanced aren't stresses minimized. I'm very confused.
My half-educated guess is that the added weight on the 7M would put more stress on bearings at higher engine speeds, but if it is properly balanced aren't stresses minimized. I'm very confused.
The lower "redline" is just on the tach it really doesn't have anything to do with the actual crank.
(I "think" the hardcut limit is lower but this seems to vary car to car)
I was running a stock weight 7M crank to 8300 with no ill effects.
Not really sure why Toyota decided to change the Tach, the 7m crank from memory is 6 lb's heavier.
(I "think" the hardcut limit is lower but this seems to vary car to car)
I was running a stock weight 7M crank to 8300 with no ill effects.
Not really sure why Toyota decided to change the Tach, the 7m crank from memory is 6 lb's heavier.
yep, lower in the ECU as well...
Maybe there was a harmonic at that speed that they found in testing? We can't really know, but they certainly had a hell of a lot more money and time to test it...
Maybe there was a harmonic at that speed that they found in testing? We can't really know, but they certainly had a hell of a lot more money and time to test it...
Yeah, but knowing Toyota there was a reason...
Doubt there is any documentation left that would shed some light on it, kinda sucks as I'd like to know myself...
I need to drive a 7M crank car to see what the difference is...
Doubt there is any documentation left that would shed some light on it, kinda sucks as I'd like to know myself...
I need to drive a 7M crank car to see what the difference is...
I ran both cranks in the same motor within 2 weeks with the crank being the only change, what do ya want to know?
i have both cranks, although i havent used them both. it seems like if they are both balanced there wouldnt really be any difference. except that the 6m crank would be a tad bit more responsive because of its lighter weight.
7M was smoother from idle to around 7000, over 7000 there wasn't much difference.
6M spins up much faster.
I ended up pulling 6 Lb's out of a 7M crank to get the best of both worlds.
6M spins up much faster.
I ended up pulling 6 Lb's out of a 7M crank to get the best of both worlds.
Somewhere I heard (maybe my mechanic) that the 7M crank had a better
average on fuel consumption...which is cause of the more balanced and
2 more counterweights and generally heavier 7M crank.
Also the 7M idles smoother and a little bit lower on rpms (100 rpms lower
than the 6M)....But the 7M like you all said has a lower redline :naughty:
Don't have a clue on why Toyota did that...:nono:
Like IJ says....My Greek calculator says that there could be a reason
that toyota's mechanics voted for that change so they can lighten up the stress on
the rod & crank bearings. We must not forget that from birth the M motor
was (since the 'Acropolis' was made) first made as an N/A engine.
3M,4M,5M,6M till 7M 1986 all were naturaly aspirated engines.The 6M-GTE
turbo engine was toyota's experiment on 6 inline turbocharged engine...with very
low production and only in the Japanese market.Toyota didn't have the time and
history/data logging on the forced induction environment.You need many
thousands of motors running on normal production cars for at least 5-6 years so
you can get a clue what is going on! ...Which happened with the 7M-GTE.
I also think Toyota (sector 7M-GTE mechanics) was a little afraid of boosting
hard the 7M.... there goes the low boost of the CT-26 (6.8 psi is a joke)
I think toyota was planning an 8M-GTE twin turbo future motor for the mk4 supra,
but after many many conferences and thoughts by the mechanics on the
future supra engine they decided to make a 100% new engine which will
be based on turbocharging and forced induction by one or more turbos :sarcasm:
So the JZ motor came up as the future engine (MHG,high revving,twin turbos,
high boost endurance...high performance in generel :icon_bigg
They intended the 1JZ-GTE engine for the 4th generation supra,but they
had (then in 1990) about 3 more years to go with the mk3 supra and Toyota
wanted the best for their premier car and the 1jz-gte was on mk3s,but only
in Japan market...
Why not export?
Well,Toyota one of the biggest motor industries,had put a lot of money and
effort on the powerplant of the A70 car. So many 7M engines were built,and
they decided a policy for the export cars to have the 7M engine only.
And no wonder why the R154 trans was mated to the 1JZ,which is one
of the best transmissions made by Toyota!
The next version of the 1JZ is the 2JZ with 500cc of displacement....That
is the story so far...
average on fuel consumption...which is cause of the more balanced and
2 more counterweights and generally heavier 7M crank.
Also the 7M idles smoother and a little bit lower on rpms (100 rpms lower
than the 6M)....But the 7M like you all said has a lower redline :naughty:
Don't have a clue on why Toyota did that...:nono:
Like IJ says....My Greek calculator says that there could be a reason
that toyota's mechanics voted for that change so they can lighten up the stress on
the rod & crank bearings. We must not forget that from birth the M motor
was (since the 'Acropolis' was made) first made as an N/A engine.
3M,4M,5M,6M till 7M 1986 all were naturaly aspirated engines.The 6M-GTE
turbo engine was toyota's experiment on 6 inline turbocharged engine...with very
low production and only in the Japanese market.Toyota didn't have the time and
history/data logging on the forced induction environment.You need many
thousands of motors running on normal production cars for at least 5-6 years so
you can get a clue what is going on! ...Which happened with the 7M-GTE.
I also think Toyota (sector 7M-GTE mechanics) was a little afraid of boosting
hard the 7M.... there goes the low boost of the CT-26 (6.8 psi is a joke)
I think toyota was planning an 8M-GTE twin turbo future motor for the mk4 supra,
but after many many conferences and thoughts by the mechanics on the
future supra engine they decided to make a 100% new engine which will
be based on turbocharging and forced induction by one or more turbos :sarcasm:
So the JZ motor came up as the future engine (MHG,high revving,twin turbos,
high boost endurance...high performance in generel :icon_bigg
They intended the 1JZ-GTE engine for the 4th generation supra,but they
had (then in 1990) about 3 more years to go with the mk3 supra and Toyota
wanted the best for their premier car and the 1jz-gte was on mk3s,but only
in Japan market...
Why not export?
Well,Toyota one of the biggest motor industries,had put a lot of money and
effort on the powerplant of the A70 car. So many 7M engines were built,and
they decided a policy for the export cars to have the 7M engine only.
And no wonder why the R154 trans was mated to the 1JZ,which is one
of the best transmissions made by Toyota!
The next version of the 1JZ is the 2JZ with 500cc of displacement....That
is the story so far...
JustAnotherVictim
Supramania Contributor
MA70witBoost
Registered Drifter
IJ, you think the 7M crank is the way to go? I have a brand new 6M crank that i got for my 87 that i ended up not using because the block was no good. Got a 89+ 7M that should have a 7M crank in it. Got both, want the best performance.
"Best performance" well that depends on your definition of best.
The 6M WILL spool/accelerate faster due to less mass but as I said it'll be a little "harsh", this harshness has to have a long term affect on bearing life but the average 7M here doesn't seem to run all that long so not a prob
Having the 6 Lb's removed from the 7M crank isn't cost effective but is a great mod if you have the $$$.
The 6M WILL spool/accelerate faster due to less mass but as I said it'll be a little "harsh", this harshness has to have a long term affect on bearing life but the average 7M here doesn't seem to run all that long so not a prob
Having the 6 Lb's removed from the 7M crank isn't cost effective but is a great mod if you have the $$$.
IJ.;1094763 said:
Did you do this yourself? Got any pictures of it/description of what you did? I have access to plenty of machinery if it were possible for me to do it. OR if you think an engine machine shop would have to do it, I know plenty of people that could get it don't for a very reduced cost I'm sure.
Any more info you could give would be very appreciated! I'm looking to put down some serious power in the next year and would like to be happy with the build of my bottom end.
Thanks!
Top prepped 6M, next prepped 7M, then the Lightened 7M.
I had my crank shop do it on the CNC, we used a Cosworth profile to remove the maximum amount but retain the inherent balance.
[thumb]http://ij.supramania.com/crank01.jpg[/thumb]
[thumb]http://ij.supramania.com/crank02.jpg[/thumb]
[thumb]http://ij.supramania.com/crank03.jpg[/thumb]
I had my crank shop do it on the CNC, we used a Cosworth profile to remove the maximum amount but retain the inherent balance.
[thumb]http://ij.supramania.com/crank01.jpg[/thumb]
[thumb]http://ij.supramania.com/crank02.jpg[/thumb]
[thumb]http://ij.supramania.com/crank03.jpg[/thumb]
It is a very difficult job to chop and reduce weight from the crank :nono:
Only if you know exactly what are you doing,and have the best and precise
machinery...then you can procide :sarcasm:
Only if you know exactly what are you doing,and have the best and precise
machinery...then you can procide :sarcasm:
IJ is one of the rare people to do this kind of things....:sarcasm:
...and he has a lot of crankshafts to play with :icon_bigg:biglaugh::biglaugh:
...and he has a lot of crankshafts to play with :icon_bigg:biglaugh::biglaugh: