JUN GT SURGE TANK FOR FT86/BRZ

[GrimmSpeed]

Originally Posted by Captain Snooze

I would have thought that the net length of the runners is about the same. Short JUN runner plus blocks equals same length. I am not disputing the graph, I just don't understand how the result has been achieved.

Knowing the diameter of the runners would be important to make this comparison, but just visually we can assume they are similar.

But the length of the runners on the JUN manifold appear to be around 4 inches shorter than the OEM manifold. And the "powerblocks" are only about an inch tall, so the net change isn't a wash, it is still a substantially shortened runner which may explain some of the top end gains.

Chase
Engineering

[Captain Snooze]

Originally Posted by GrimmSpeed

But the length of the runners on the JUN manifold appear to be around 4 inches shorter than the OEM manifold. And the "powerblocks" are only about an inch tall, so the net change isn't a wash, it is still a substantially shortened runner which may explain some of the top end gains.

Thank you. I can sleep tonight.

[Tokay444]

The intake with spacers makes more power in the same rev range.

[stevo_12v]

JUN Instruction Manual




Closeup of the goodies


HKS Racing Single exit


Picked up the car this morning. Car definitely loves being in the higher RPM range. Power doesn't taper off as it used to in the higher revs.

[nikitopo]

This intake manifold is designed for a high revving NA engine. You'll need to build now the engine with their forged aluminum piston kit and their rods. The pistons are build in Capricorn Germany and they increase the compression ratio to 13.0:1. I am sure that after the engine build, you'll have the strongest NA build running on pump gas. Forget all these guys trying to build such a car the last 3-4 years. They're just promising all these years and still have nothing.

Btw., I don't agree to install a turbo. Your changes are focused more for a NA setup .

[Spartarus]

Originally Posted by Captain Snooze

No, I am totally lost.
Photo shows a positive gain in the power curve. Win.
BUT as @x808drifter and @churchx says, and the part that messes with my head, I would have thought that the net length of the runners is about the same. Short JUN runner plus blocks equals same length. I am not disputing the graph, I just don't understand how the result has been achieved.

Let me clarify.

The powerband didn't change at all, the shape is identical. It just moved up in the rev range. That is all.

Peak torque didn't appreciably change, I don't have to see the graph to know that. Again, it shifted it higher in the rev range, and the power gains are proportional, because power = torque x speed / constant.

JUN runners are very short. Add blocks, they are still shorter, just not super short.

I'd bet money, if you pulled the blocks, peak torque would move up another 300-400 RPM, and peak power would follow it on up.. Shorten the runners, the powerband will move up again, unless the plenum volume or throttle diameter becomes insufficient. That will eventually kill torque. You can't push it up forever.

They didn't show the torque curve, but here's the relevant point:

OLD peak power: 190 @ 6400 RPM
OLD peak torque, calculated: 155.9 ft/lbs

NEW peak power: 201.9 @ 6700 RPM
NEW peak torque, calculated: Drumroll please.... The very same 155.9 ft/lbs

The car will be faster, reflected in the peak power increasing, but torque didn't change.

I'm thrilled with the outcome of this experiment. Thanks OP, enjoy your money well spent. Yes, the HP/$ ratio isn't stellar, but there's something special about NA power, especially since nobody else has been successful in making much of it.

Originally Posted by Spartarus

If max VE, and therefore max torque, stays the same, but moves higher in the Rev range, the percent increase in horsepower will be proportional to the percent increase in RPM for peak torque, because of how horsepower is calculated.

It's not magic, it's physics. There are rules. They are absolute. Doesn't mean they are well-understood.

Originally Posted by GrimmSpeed

Knowing the diameter of the runners would be important to make this comparison, but just visually we can assume they are similar.

If I looked only at the dyno chart, and never saw photos, I'd assert that the diameter is (near-as-makes-no-difference) identical to OEM. (Average diameter, compared by runner circumference / pi, because of shape differences... But I'd bet the number is within 5mm either way.)

I will disclaim that this is ballpark math from looking at the graph, and there may be small variations if it's done more precisely, nothing is perfect in the real world, but It's close enough to make the point.

[stevo_12v]

Originally Posted by Spartarus

Let me clarify.

The powerband didn't change at all, the shape is identical. It just moved up in the rev range. That is all.

Peak torque didn't appreciably change, I don't have to see the graph to know that. Again, it shifted it higher in the rev range, and the power gains are proportional, because power = torque x speed / constant.

JUN runners are very short. Add blocks, they are still shorter, just not super short.

I'd bet money, if you pulled the blocks, peak torque would move up another 300-400 RPM, and peak power would follow it on up.. Shorten the runners, the powerband will move up again, unless the plenum volume or throttle diameter becomes insufficient. That will eventually kill torque. You can't push it up forever.

They didn't show the torque curve, but here's the relevant point:

OLD peak power: 190 @ 6400 RPM
OLD peak torque, calculated: 155.9 ft/lbs

NEW peak power: 201.9 @ 6700 RPM
NEW peak torque, calculated: Drumroll please.... The very same 155.9 ft/lbs

I forgot to add this photo, thought I put it up, but must have been on my FB page. Has the torque marked on this

[Spartarus]

For somebody who likes to run right up to the rev limiter, that is some fat area under the curve at the top.

Peak is off less that 2 n/m from the looks of it... less than 1 foot pound difference, so the math holds up.

The jungle below 5000 rpms is always interesting in these cars... This is a funny little engine.

If you get it to 8k eventually, hanging on to a lower gear for an extra several hundred RPM is transformative, especially if the powerband holds up.

[Captain Snooze]

Originally Posted by Spartarus

JUN runners are very short. Add blocks, they are still shorter, just not super short.

Thank you for the detailed explanation.

[Teseo]

Originally Posted by stevo_12v

I forgot to add this photo, thought I put it up, but must have been on my FB page. Has the torque marked on this

Man... any chance you can do video on the dyno?
Also want to see the tachometer near on 9k rpms, will be porn of NA's crew

[stevo_12v]

Originally Posted by Teseo

Man... any chance you can do video on the dyno?
Also want to see the tachometer near on 9k rpms, will be porn of NA's crew

Possibly. Thinking of changing back to my Spec-L as its alot quieter and I prefer the exhaust note. Plus I think I might be losing HP staying with the single exit.

[GsxrMe]

JE has 13.5:1 pistons you might want to think about for your built NA car. Ive used them in my turbo busa and nothing but fantastic results.

http://www.jepistons.com/Catalogs/Sp...baru/fa20.aspx

I hope to see you qt 230bhp or ill be sad

[Cybmx]

Originally Posted by stevo_12v

Possibly. Thinking of changing back to my Spec-L as its alot quieter and I prefer the exhaust note. Plus I think I might be losing HP staying with the single exit.

Hi Stevo, what kind of reverse light is that? Could you post a link to that light? I like it quite a lot. TIA

[nikitopo]

Originally Posted by GsxrMe

JE has 13.5:1 pistons you might want to think about for your built NA car. Ive used them in my turbo busa and nothing but fantastic results.

Are these build to handle boost or high revs? There is a difference between these two things.