7M short block strength in high torque applications in question.

[InFrnt0fU]

I did some searching on google to see if I could find any information on the longitudinal rigidity of inline piston type engines and came up with nada.

My question is...Are there any draw backs in the physical design of inline piston engines (7M NA block specifically) in highly stressful situations (high revs, high torque out, higher temps from turbos)?

My guess would be no because an engine that is putting out big torque numbers for longer amounts of time (think engine stress in drifting conditions) is very well built internally.

Hopefully I'm not completely off the rocker asking this.

 

[GrimJack]

These blocks have been stressed to higher than you will ever go without breaking.

Have a peek here: http://www.gtepowered.com/index.php?page=html/gcurmi/profile.php

 

[ft413]

damn! good to know!

 

[IJ.]

They won't "break" but they DO move around a lot

I was seeing some seriously funky Main bearing wear patterns a couple of years back when I experimented with sustained high RPM runs.

 

[Poodles]

Large diesels are inline for a reason...

 

[InFrnt0fU]

I was seeing some seriously funky Main bearing wear patterns a couple of years back when I experimented with sustained high RPM runs.

Good to know. If you could IJ, can you describe what you mean by "funky" any further? And how high of RPMs are you talking about. I'm guessing around 8-9k.

 

[IJ.]

I was seeing wear on the outside edges of the bearings but not in the middle, only explanation I had was at tight clearences it was flexing both the crank and the block enough to shear the oil wedge at the edges.

Opened up the clearences a little and it's been fine.

8300>8500 daily

 

[Supra28]

^ 8500 RPM'd 7M sounds crazy. :aigo:

There are a lot of high powered 7M's out there, and their blocks seems to be holding up just fine.

 

[IJ.]

It sounded AWESOME if you had enough In/Out flow so it would still make power up there

 

[InFrnt0fU]

It sounded AWESOME if you had enough In/Out flow so it would still make power up there

Looking forward to hearing the 'AWESOME' in my car in a couple of years.

Was there anything else abnormal when doing the sustained high rpm runs other than the odd wear you experienced?

I'm trying (budget in mind) to use the lightest and strongest parts out there for the internals in my twin turbo build, definitely not cutting any corners there, so I don't think I should have any problems.


7M torque + twin dbb turbos = oh yes please and hopefully bye bye turbo lag.

 

[toy fanatic78]

Twins,Why?

 

[InFrnt0fU]

Twins,Why?[/QUOT

Cause I want to build power using twins not a big single. That reason is good enough for me. - I personally think twins are better...less lag, and better ability to tune to the torque/hp curve you want. I don't mind paying extra for having the car drive exactly like I want it to. Why ask why?

 

[toy fanatic78]

Twins,Why?[/QUOT

Cause I want to build power using twins not a big single. That reason is good enough for me.

A lot of people talk about a twin 7M setup, I haven't seen too many finished yet.Just a lot of fabrication and extra money to run a twin setup when,even with a moderate sized single,you can push over 400 rwhp.IMO on a streeted supra much over 500 hp is kind of a waste due to traction issues(see IJ's build)IIRC his is ~470 rwhp and his traction control pulls throttle when he pushes it hard.

 

[InFrnt0fU]

A lot of people talk about a twin 7M setup, I haven't seen too many finished yet.Just a lot of fabrication and extra money to run a twin setup when,even with a moderate sized single,you can push over 400 rwhp.IMO on a streeted supra much over 500 hp is kind of a waste due to traction issues(see IJ's build)IIRC his is ~470 rwhp and his traction control pulls throttle when he pushes it hard.

Horsepower has nothing to do with why I've chosen a twin setup versus a single. I'm not building a dyno queen. http://www.supramania.com/forums/showthread.php?t=84889

That is the link to my build thread. Maybe the build spec sheet will give you more of an idea of what I'm trying to accomplish.

 

[GuNDeZZZ]

IJ is that 7M's build on this site???

 

[Nick M]

Twins,Why?[/QUOT

Cause I want to build power using twins not a big single. That reason is good enough for me. - I personally think twins are better...less lag, and better ability to tune to the torque/hp curve you want. I don't mind paying extra for having the car drive exactly like I want it to. Why ask why?

Because you want to is all the reason you need.

But your other reasons listed isn't true.

If you add a second CT26 to an existing setup, it will spool slower. Same with any turbo. Adding another slows down the response. You have half the cylinder heat driving the turbine. It isn't debatable.

Adding a qualifier or three can change that. Such as running smaller turbos. Running any smaller turbo will increase response, and decrease total airflow. Running a second of any turbo changes that. Twins were done in the past because a true T04 on a small engine does take too long to respond on a street car.

 

[Nick M]

Large diesels are inline for a reason...

Like a Detroit Diesel?

 

[toy fanatic78]

Horsepower has nothing to do with why I've chosen a twin setup versus a single. I'm not building a dyno queen. http://www.supramania.com/forums/showthread.php?t=84889

That is the link to my build thread. Maybe the build spec sheet will give you more of an idea of what I'm trying to accomplish.

I was just curious as to why you chose twins.Wasn't knocking your build or anything.Good luck with it.What do you plan to do as far as suspension/brakes and chassis mods?

 

[IJ.]

Looking forward to hearing the 'AWESOME' in my car in a couple of years.

Was there anything else abnormal when doing the sustained high rpm runs other than the odd wear you experienced?

I'm trying (budget in mind) to use the lightest and strongest parts out there for the internals in my twin turbo build, definitely not cutting any corners there, so I don't think I should have any problems.


7M torque + twin dbb turbos = oh yes please and hopefully bye bye turbo lag.

Had some trouble keeping valve springs in it, I broke one and sacked out another 3 but Cryo treating them and not revving it as had has solved that issue.

If you're hellbent on twins I'd rob a set of a 2J upgrade the turbo's to something better and keep the full sequential system.

 

[Poodles]

Yep, non-sequential twins are lag monsters...

Local guy has the HKS twins on his MKIV and the lag is horrible. Going with a large, single, MODERN, ball bearing turbo would be an upgrade for him (and he's thinking about it last I knew).