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

[7Mboost]

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 clearances a little and it's been fine.

8300>8500 daily

 

[tekdeus]

I'm building an inexpensive sequential single turbo system with the SP Quick Spool Valve (you can search here for info). Coupled with one of the new DBB billet turbos or modified GT series turbos with extended tip billet compressor, should really expand the powerband in both directions. Faster spool, more power from the higher flowing lighter ETT billet wheel based on the Borg Warner turbos.

 

[Nick M]

I'm building an inexpensive sequential single turbo system with the SP Quick Spool Valve (you can search here for info). Coupled with one of the new DBB billet turbos or modified GT series turbos with extended tip billet compressor, should really expand the powerband in both directions. Faster spool, more power from the higher flowing lighter ETT billet wheel based on the Borg Warner turbos.

Real sequential, or not really sequential, like Toyota did?

 

[tekdeus]

Real sequential, or not really sequential, like Toyota did?

http://www.supramania.com/forums/showthread.php?t=85016

 

[dumbo]

Like a Detroit Diesel?

hhmmm Cummins..
http://www.youtube.com/watch?v=cV0XJePUitI

 

[InFrnt0fU]

hhmmm Cummins..

What a wonderful sound that is.

 

[Nick M]

Detroit Diesel is the number one selling heavy duty powerplant in the world. I think. Thanks in part to the US Army. That was the point to my comment.

 

[dumbo]

Detroit Diesel is the number one selling heavy duty powerplant in the world. I think. Thanks in part to the US Army. That was the point to my comment.

i was just talking about a specific inline 6 block.

 

[Terrh]

well since this thread is now TOTALLY off topic anyways (how strong is the stock block) I'll post a comment regarding twins:

while a single modern BB turbo will certainly outperform a pair of old, crappy, 70's era twin turbos,

below 600HP and where "lag" is an issue (most turbo lag is in your head anyways) it's pretty hard to outperform twin non-sequential turbos. Sequential is even better, but good luck rigging that setup up. There's a reason why nobody does it anymore, and why only a few companies (toyota and mazda are it afiak) did it in the first place..

I don't have much experience with the 7M yet, I just bought my first MK3 supra less than a week ago, but I do have a large amount of experience with another stout inline 6: Nissan's RB26.

I think if you're shooting for a moderate amount of horsepower, say somewhere in the 500-600 range, it'd be hard to beat a pair of GT28R-5's if you're trying to make peak torque early and have a big powerband.

Twins aren't a whole lot more complicated anyways, you just build 2 small manifolds instead of one giant one. If they're internally wastegated (as GT28's are) that's easy to deal with, all you need to do is some more exhaust plumbing (or run a dual setup) and a bit more pre intercooler piping, or run twin inlets into the I/C.

 

[Nick M]

while a single modern BB turbo will certainly outperform a pair of old, crappy, 70's era twin turbos,

Two turbos never respond faster than one.

below 600HP it's pretty hard to outperform twin non-sequential turbos.

Sorry, that isn't true at all. Parallel is the slowest responding.

There's a reason why nobody does it anymore, and why only a few companies (toyota and mazda are it afiak) did it in the first place..

Toyota wasn't sequential. That means one then the other. They did one then both on the 2JZ. They ran one for down low because it responds faster than running both at the same time. Yes, there is a reason they did it, and it goes against your point above.

 

[Nick M]

Large diesels are inline for a reason...

I want to go back to this correct comment for a moment. They are also inline because of the huge advantage in manifold flow and layout.

 

[Terrh]

Two turbos never respond faster than one.



Sorry, that isn't true at all. Parallel is the slowest responding.




Toyota wasn't sequential. That means one then the other. They did one then both on the 2JZ. They ran one for down low because it responds faster than running both at the same time. Yes, there is a reason they did it, and it goes against your point above.

Parallel turbos /are/ the slowest responding of twin setups - but they're far from slow, and they'll still outperform a single. You've got less turbo inertia, and therefore faster spool times. Why do you think nissan, porsche, etc use twin turbos instead of just one? They sure aren't saving money.

I suggest you look up the definition of sequential turbocharging here: http://en.wikipedia.org/wiki/Twin-turbo

Here's another very informative page about how the sequential turbo system works on the 2JZ-GTE:
http://www.max-boost.co.uk/max-boost/supra/turbo.htm

I did some googling and could not find any car that uses a system that shuts the primary turbo off after spooling the secondary. Maybe big diesels use them or something, but I couldn't find anything or anyone that does it that way, I believe the wikipedia definition to be accurate.

My RB26 with it's twin parallel turbos sees full boost by 2500RPM and made over 400WHP, on its turbos designed in the 80's. If I put some modern ones on it (as I will be doing over this winter) it'll still see peak torque around 4000RPM and peak horsepower numbers in excess of 700whp. There are very few single turbos that could deliver that type of performance, if any.

 

[Nick M]

Considering I have the Toyota manual at home descirbing the two way turbo on the 2JZ works, I will pass on a wiki article.

Try this, since you don't seem to get it. If you take that twin GT28, and remove one, running all 6 into it, will it respond faster or slower than two?

Just so you know, I didn't say that running one, then the other is a good idea. Or that Toyota does it.

 

[Terrh]

Considering I have the Toyota manual at home descirbing the two way turbo on the 2JZ works, I will pass on a wiki article.

Try this, since you don't seem to get it. If you take that twin GT28, and remove one, running all 6 into it, will it respond faster or slower than two?

Just so you know, I didn't say that running one, then the other is a good idea. Or that Toyota does it.

OFC a single GT28 would spool faster than a pair of them. But it'll only make half the power as it's half the size, what do you expect? My point is that two smaller turbochargers sized to match a bigger single, the twins should spool earlier.

So if you take and plumb all of your cylinders into a single GT42, or a pair of 28's, the pair of 28's should be the better performer.



I know you didn't say that toyota does it that way, but you said that's how it's defined, and it isn't. Nobody does it that way, because it'd be difficult to do, and there's zero benefit to doing it.

 

[Nick M]

You still don't get it. You want to claim that twins spool faster. To do so, you use evidence of different sized turbos. That has nothing to do with adding another turbo. A second turbo slows down response.

I am done with this one. For now.

 

[Terrh]

I think there's something being miscommunicated here for sure.


if you want 400 horsepower, and one turbo, you use 1 400 HP capable turbo.

If you want 400 horsepower, and two turbochargers, you use 2 small 200hp capable turbos.

Why would you use 2 big ones when 2 small ones would do the job? Of course 2 big ones are going to spool slower than 2 small ones, that's obvious!

But 2 small turbochargers will spool earlier than one equivalently sized big one.

Your argument isn't making any sense - do you see what I'm saying here? Nobody's going to put a second GT42 on their car and think things will spool faster than before, that's impossible. But if they put two smaller turbos that will make the same power as one GT42, you'll have more response and an earlier spool.

 

[IJ.]

Actually you'd need 2x 220's

 

[Poodles]

It's been proven wrong. The HKS twins are lagmonsters from hell...

The MKIV's system is amazing, and gives a HUGE torque curve that is hard to beat because of the system they use. Without this system the lag is very obvious (there are plently of dyno sheets on SF showing the change).

Not only that, you have piping issues, space issues, oil supply, drain... not to mention the most important.... COST.

One great, modern turbo is going to be cheaper than two turbos, and that's JUST the cost of the turbos.

Are twins cool? Yes. Are they worth it in this day and age with modern turbo design and engine management (antilag)? Hell no.

K.I.S.S.

 

[Terrh]

nobody uses antilag on the street, aside from maybe for launches, unless they want to replace turbine wheels on a monthly basis. (if not sooner, depending on how its driven).

What HKS twins are lagmonsters, and where'd you hear that? And what's the reason for them being laggy?

If nissan, porsche, toyota, etc all thought that a single turbo would be better, why did all of them go twins? Why did bugatti use FOUR?

why do most semi trucks in the 500+hp range use twins instead of a single? Why do those trucks make peak torque 20-30% earlier than even weaker single turbo trucks?

it's because twins kick ass. Singles work well, but you can't say that they will outperform twins in every case because that's simply wrong.

 

[Poodles]

Semi's don't use twins like a gasoline engine, they're compound...

Where did I hear it? Only from the local that has em on his MKIV and was going single so he had some kind of useable powerband.

Why do they put crossdrilled rotors on modern cars?