15-17 intake manifold improvements?

[1MeanZ]

Anyone that's looked at the power curves of the stock 15-17 manifold vs the '18+ or GT350 manifolds can see that the 15-17 intake is better until 6500rpm. I think the ideal scenario for many of us with street cars would be to find a way to port the 15-17 manifold to get another 500+rpm out of it. If you could get the 15-17 manifold to make equal power to the 18 manifold at 7000 rpm but still make more power down low that would be the win-win in my opinion.

So the question is, does anyone know in detail the shortcoming of the 15-17 manifold? Is it runner length too long? Can it be ported? I've looked everywhere and I can't find anything on modifying a 15-17 manifold, everyone dumps them for the 18+ or GT350. If anyone has a 15-17 manifold they want rid of, PM me and I'll pay shipping. I'd like to try to modify one and see what happens...

Sponsored

 

[5.0_SD]

One in the marketplace... https://www.mustang6g.com/forums/threads/15-mustang-manifold.144680/

 

[chagan02]

Anyone that's looked at the power curves of the stock 15-17 manifold vs the '18+ or GT350 manifolds can see that the 15-17 intake is better until 6500rpm. I think the ideal scenario for many of us with street cars would be to find a way to port the 15-17 manifold to get another 500+rpm out of it. If you could get the 15-17 manifold to make equal power to the 18 manifold at 7000 rpm but still make more power down low that would be the win-win in my opinion.

So the question is, does anyone know in detail the shortcoming of the 15-17 manifold? Is it runner length too long? Can it be ported? I've looked everywhere and I can't find anything on modifying a 15-17 manifold, everyone dumps them for the 18+ or GT350. If anyone has a 15-17 manifold they want rid of, PM me and I'll pay shipping. I'd like to try to modify one and see what happens...

This. I wanna believe in the 18 manifold but I don’t want to sacrifice all that low/mid torque. Especially on a streetcar, and the fact of spending $500 to lose performance over 3/4 of the power band. Very good question you have about porting the stock 15-17 manifold.

 

[Nuked]

18+ manifold with some kind of spacer on the runners? Add to runner legnth and help with low end some? Just spitballing.

 

[chagan02]

18+ manifold with some kind of spacer on the runners? Add to runner legnth and help with low end some? Just spitballing.

Interesting....

 

[1MeanZ]

18+ manifold with some kind of spacer on the runners? Add to runner legnth and help with low end some? Just spitballing.

I hear you there, that's one of my questions. We don't even know the difference in runner length between the 2 manifolds, if there even is any.

Ultimately we can't change runner length, so the power peak will likely stay where it is in the RPM range. However if we can increase the flow such that the peak power is higher and there is less of a HP loss compared to the 18+ manifold at 7000rpm then we're really got a winner.

I guess it is possible that there is some sort of restriction causing the HP loss at 6500 and removing it would flatten the drop off after 6500, but it's not the 70s or 80s anymore, I highly doubt there is some casting lump in the middle of a port on these modern manifolds.

 

[Nuked]

I hear you there, that's one of my questions. We don't even know the difference in runner length between the 2 manifolds, if there even is any.

Ultimately we can't change runner length, so the power peak will likely stay where it is in the RPM range. However if we can increase the flow such that the peak power is higher and there is less of a HP loss compared to the 18+ manifold at 7000rpm then we're really got a winner.

I guess it is possible that there is some sort of restriction causing the HP loss at 6500 and removing it would flatten the drop off after 6500, but it's not the 70s or 80s anymore, I highly doubt there is some casting lump in the middle of a port on these modern manifolds.

Runner legnth is shorter on the 18+, not by much but enough to shift the power band to the right some. I think the key to the 15-17 is what exactly the differences are between the Gen2, Gen3 and GT350. GT350 seems to be the best and a combination of the two. Aside from the inlet diameter, what else does the 350 have that the other two don't?

 

[MyStang]

1MeanZ,
This is exactly the kind of information I have been looking for, except I have been searching for ported 2017 F150 info for the same reasons. Looks like I'm going to bite the bullet and send it in for porting. With the power pack 2 they estimated 450 crank and 398whp. I have a manual with 3:31 and on the dyno, they can't get an accurate pull in 5th. They tried a 4th gear pull and would hit the 116 MPH speed limiter.

 

[EFI]

You're probably better off porting an 18 manifold to gain back some lost low end.

Matching low end with better top end is the bigger win.

 

[WildHorse]

18+ manifold with some kind of spacer on the runners? Add to runner length and help with low end some? Just spitballing.

Well dunno how the injectors would fit with spacers under the runners. Anyways, Old School is still relevant, you need to add plenium volume. So, what's the easiest way to do that on a 15-17 manifold? 1/2" or thicker TB spacer. You'll get close to the 18 volume and your peaks should move up 500 rpm give or take. Cheers.

 

[bauern]

I hear you there, that's one of my questions. We don't even know the difference in runner length between the 2 manifolds, if there even is any.

https://www.hotrod.com/articles/dyno-every-ford-coyote-intake-manifold-on-gen-3-crate/
Runner length, cross section, total volume and visual comparison.

 

[1MeanZ]

You're probably better off porting an 18 manifold to gain back some lost low end.

Matching low end with better top end is the bigger win.

I'm not sure how to do that? Usually torque is aided by port velocity and runner length, I'm not sure how to boost those by porting an existing manifold. With the Gen 2 manifold I already have the mid-range power, I just need to get a little better flow up top. Again, I don't think it's possible to change the rpm where the peak power exists by more than 1-200 rpm, but if I can increase the overall flow I may be able to gain enough across the board to match the other intakes.

I'm still just shocked at how little info there is for the Gen 2 manifolds. I can't find anything on them...

https://www.hotrod.com/articles/dyno-every-ford-coyote-intake-manifold-on-gen-3-crate/
Runner length, cross section, total volume and visual comparison.

Good article but absolutely nothing on the 15-17 Gen 2 manifold. No port volumes or anything listed. Would have been good to see those published for the F150 manifolds and the Gen 2 manifold.

 

[Nuked]

Well dunno how the injectors would fit with spacers under the runners. Anyways, Old School is still relevant, you need to add plenium volume. So, what's the easiest way to do that on a 15-17 manifold? 1/2" or thicker TB spacer. You'll get close to the 18 volume and your peaks should move up 500 rpm give or take. Cheers.

Yeah you would have to figure something out there. I thought about the TB spacer as well, my biggest question though was if it works why hasn't anyone made one? TB spacer isn't rocket science, I agree with you on it adding plenum volume, I just wonder why it hasn't been done.

 

[WildHorse]

TB spacer isn't rocket science

I gotta friend with a 3D printer.. he could prolly make a 1" thick spacer outta plastic. I'll ask him.

 

[Nuked]

I gotta friend with a 3D printer.. he could prolly make a 1" thick spacer outta plastic. I'll ask him.

What would be nice is one that corrected the angle on the 18+ manifold.

Sponsored