2867 would make the same power and a lot more mid-range. Nice peak numbers.

 

2867 would immediately toll the death knell for this motor.

 

Awesome numbers, thanks for sharing. Definitely makes me feel more comfortable about pushing my motor a little harder.

 

Impressive to say the least. Never have seen numbers like this on a stock bottom end.

*heads to garage and turns boost **** to eleven

 

That's definitely a lot of power for stock internals. The reason there's not a rod through the side of the block is that it's a laggy setup. Lots of low down torque is what kills stock rods. So a smaller turbo spiking high boost will create a lot of torque down low which is what kills stock motors..

So his setup is provably more ideal for making "good" peak hp. Without building the motor. The problem is that lots of down low torque is what makes a car fun!!

 

Where's the video?

 

I was thinking the same thing.

 

Its not so much the torque down low that kills the rods, but the combo chamber pressure. This power number is actually kind of believable more because of the huge monster sized turbine section on that turbo than just the lack of low end torque. I do not believe it will last long, but only 280ftlbs, e85 with its slower flame front speed, and the huge turbine makes the hp number on the stock block believable. Still its a race to see if the 5 speed or the rods give out first. It probably starts to spin as soon as the boost comes on in 3rd gear so it might not immediately grenade the 5 speed.

 

Why does torque down low kills rods as apposed to the same torque at a higher RPM level? I'm not saying you're wrong or anything. I've just never heard this before.

 

At lower speeds the cylinder pressure gets high earlier in the downstroke and the rod has very little leverage to make use of it, so the rod gives. If the cylinder pressure peaks when the rod is getting closer to being 90 degrees to the crank throw then it can make better use of the force because of it's leverage advantage. In the first example it really is binding up the energy with no place to go, mostly. This is another way that e85 helps - slower burn so the peak happens later.

 

So it has to do with of time the peak pressure is held and rod angularity at peak pressure. Makes sense.

 

Sixshooter explained it well. Cylinder pressure definitely has an effect. Torque is the actual force that your motor is providing. which is what strains the components, not not the measure of said force over time, which is what your measuring with Horsepower. Torque kills motors. Drive train. Rear diffs etc.

If the OP had the same turbo but in a dual ball bearing form and/or a twin scroll turbo manifold. He would see full boost anywhere from 500 to 1k rpms sooner. And probably see at least 50wtq increase maybe more. Thus putting more stress on the rods down low.

Have you ever had a clutch start to slip on you? At first it only slips in high gears. Say 4th thru 6th. This is due to engine load(or torque) your car can't produce enough torque in 1st gear typically to make your clutch slip(when it first starts slipping lol).

A great benefit the OP has is that he is running e85. (Great fuel as I run it in my evo 8.) allows you to safely turn up the boost(due to higher octane, think racing fuel) and it has a cooling effect that also helps with detonation.

On my gt3076 evo. I went from 390awhp on 25psi. To 460awhp on 30psi. Just from the fuel.

 

I have a TII trans and I don't expect that to blow up. I have a Built motor that will be going in soon and I will downsize to a smaller turbo also like gtx2871 and that should be fun

 

HomemadeWRX has some EFR's for sale in the classifieds. You might consider picking up one of them. I got one to do some back to back testing with my GT2871.

 

This is the first time I have seen this explained in a manor that makes sense! I have always heard that lots of boost low in the RPM band (i.e. lots of low end torque) will destroy stock internals on a Miata, and had seen lots of empirical evidence here on the board for this being true, but until now hadn't seen a realistic explanation of WHY it is true.

Thanks,

Keith

 

Most equate cyl pressure to lowend grunt. Often related, but not always. But yeah, shooter sums it up well, I guess we all just kinda assumed that this was common knowledge (hence no discussions about it). I don't claim to know all about it though, don't get me wrong.

In the case of e85 is where I'm guessing the two are not related, since you don't give up any lowend grunt, yet somehow are easier on cyl pressure

 

Peak cylinder pressure vs average cylinder pressure.

 

Not to threadjack, but one could likely get away with big boost at lower RPMs on pump gas with stock rods if the ignition event was sufficiently delayed. Peak pressure retard saves rods.

 

Bought one of these:


(GTX2867 T3 .63AR exhaust housing, vband outlet)

One of these:



and one of these:



All going on a built motor with 8.5:1 compression

 

Does your ECU not do EBC?