Porting the stock Intake manifold (my write up)

[greenberet]

Wow - thanks for that. The dyno run CB169 did without the VVIS plate generated a torque curve that looks like yours - no hump between 3000 and 5000 rpm and the same shape on the top end.

The three horsepower curves from your dyno sheet show something like
- 3.5 horsepower gain at 7800 rpm with a gutted VVIS plate or without a VVIS plate
- 11.5 horsepower loss at 4300 rpm without the VVIS
- the power curve with the completely removed VVIS plate looks nicer than the curve with the gutted VVIS plate.

That's only one data point and there's variation between runs, etc. but damn, based on that I'm going to rethink whether I really want to touch the VVIS plate in my n/a engine and if I do, it may be better to just completely remove the VVIS rather than gut it.

 

[96cxt]

WOW, so the people who are staying NA should keep the VVIS plate.

This dyno helps me out alot.

Thanks:biggrin:

 

[swerve2007]

why are you guys so surprised? why would honda design and manufacture such a complex device (not in manufacturing sense but in design/harmoncs) if it was a waste of time? i am guilty of it myself but the sooner you realize that you can't out-engineer the factory, the more money you will have for tires and track-days.

 

[greenberet]

why are you guys so surprised?

Read about DAL Motorsports experience with the VVIS plate in naturally-aspirated NSX engines here (click on "Intake Manifold").

 

[swerve2007]

i've seen it- the point is that it is their opinion, i don't see any proof there.

 

[Mac Attack]

why are you guys so surprised? why would honda design and manufacture such a complex device (not in manufacturing sense but in design/harmoncs) if it was a waste of time? i am guilty of it myself but the sooner you realize that you can't out-engineer the factory, the more money you will have for tires and track-days.

I don't claim to know nearly as much as the Honda engineers, but I do know that THERE IS NO PERFECT DESIGN - EVERYTHING IS A COMPROMISE.

Theoretically, the VVIS is there to serve a purpose - enhance mid-range torque. Obviously, this will have to come at some expense which is the complexity, cost of the system, and some small increase in restriction. As my daily-driver, I really don't care for a 10HP gain between 3500 and 5k RPM. I may have a numb butt, but my butt dyno isn't really going to tell a difference. Racers don't either, as their engines will mostly be at 5k RPM and higher around a course. Their intakes, cams, and headers will be tuned accordingly for that max power within the higher RPM range.

Yes, I actually find it silly that Honda spent all this time and money for what, 10HP over at most a 1500RPM range Please. Then they use cast-iron manifolds that are obviously restrictive I guess the Honda engineers aren't perfect either, or maybe they just had to work around certain restraints.

I appreciate the time and money spent by others here documenting their discoveries because it really does benefit us all. For example, on this VVIS plate, I was going to pull it apart soon as well to ensure the screws are all tight as SCORP has mentioned there may be some issues on those coming loose. At that point, I was probably going to delete it with a spacer, but may not now. I would still hone it though.

Dave

 

[swerve2007]

hello,
my comment was purely scientific, i am not demeaning anyone's efforts.

edit- i am glad that we have the dyno plots- another myth put to sleep.

 

[96cxt]

Update...

The one I ported for Scott's car has shown good results. Scott now has the Love Fab turbo kit on his NSX and Cody from Love Fab said it showed higher numbers on the dyno with the turbo kit.
We couldn't get a before and after on just the manifold on Scott's car to do a comparision before he got the turbo installed.

I should be able to free up some time this wkend and will finish porting my intake manifold and will try to get a dyno posted with the VVIS plate removed. I got a BBSC kit coming in and can't wait.

Rahim

 

[Ponyboy]

For comparision, here's mine:

 

[96cxt]

Ponyboy that looks good. Did you already install it?

 

[96cxt]

So I finally installed my ported and polished intake manifold. I omitted the VVIS completely so the manifold it self is shorter. The car pulls stronger in vtec all the way to 8k rpm. But this is usually not enough for me I wanted to see what it showed on the dyno.
Before the P&P manifold and BBTB the car made 261 whp, dynoed yesterday and with the P&P manifold and the BBTB the car made 275 whp and 201 tq.:biggrin:
Dyno sheet will be up later.

Rahim

 

[doc_tai]

very nice gain, I might do these for my car now.

 

[syam]

can you please post the before and after sheets? not sure if you were going to as you said sheet in the singular...

i would be interested to know how the butterfly assembly changed the harmonics of the intake system to make more torque in the lower rpm range.

thanks.

 

[Honcho]

I have been following this thread for a while and I have to say, Rahim, that this is very promising work! I think we need to look at a few different conditions in terms of CFM requirements.

(1) NA 3.0 to 3.2L and stock cams => Before your work, the general consensus was that the OEM intake system provides enough CFM for the engine and the flow restriction was on the exhaust side. Based on your dynos, it seems by opening up the TB and manifold, you pick up 14 peak whp. This would seem to suggest that the OEM heads and cams have some room for more airflow, though not very much. Did you experience the same loss of the mid-range power "hump" by deleting the VVIS? If so, I guess the downside consideration for mods on this engine setup is the tradeoff for mid-range vs. high-rpm power. The former makes a difference in daily driving and the latter on the track.

(2) NA 3.0 to 3.2L and "hot" (i.e., high lift) cams => It's an open question whether the OEM intake system can deliver enough CFM to supply more cam lift. Based on your dynos, it certainly doesn't appear so. I'd be interested to see what the peak and "under the curve" gains are when you add cams to the equation. Being fed by the additional CFM from your port work, it may just erase any issues with mid-rage power loss since the overall gains could be higher across the entire power band.

(3) NA 3.3 to 3.8L => Here is where it gets interesting. I think your efforts could make a big difference for those drivers with increased displacement. It would be interesting to see if even a ported intake system can't supply enough CFM. I think here the heads will likely be a problem before the intake, though. I'd love to know how much CFM the OEM heads can flow with stock and "hot" cams. What we really need is someone with access to a flow bench to test all of these combos. It would tell us where the bottlenecks are and what the limits are for mods.

(4) FI 3.0 to 3.2L => Looks like Cody already has confirmed gains on his turbo setup.

Personally, I'd like to see 300 daily drivable whp out of my 3.0L. I know it is possible with the 3.2's, but about 270 seems to be the limit for the smaller engine with I/H/E. I was originally thinking stroker, but maybe your intake mod can help those of us NA1 folks crack the 270 NA ceiling!

 

[96cxt]

can you please post the before and after sheets? not sure if you were going to as you said sheet in the singular...

i would be interested to know how the butterfly assembly changed the harmonics of the intake system to make more torque in the lower rpm range.

thanks.

Here is my write up on the Custom intake I built this shows the before and after dyno of the cold air intake on my NSX.

Here is the after dyno sheet. (sorry for the cell phone pic, can't find my cam.)

The mid range didn't seem to be affected much but you can really see the top end gains on the graph.
I have a DC sport exhaust system on the car that in my opinion is a bit restrictive then other aftermarket exhaust. I like the DC sport cause it very quiet. So with a freer flowing exhaust I think we should be able to see about 5 more whp. Also I haven't touched the tuning (fuel/timing) on the ecu, tuning will help all the add-ons make more power. I think I will get an adjustable fuel pressure regulator next to see if adding a bit more fuel will help.
Cams will definately make a good difference with this set-up but cost wise the cams are expensive. I had started a thread to find out if type-r cams are the same as na-1 or na-2 cams but didn't hear much feedback. Some one mentioned that they are the same. So if a higher lift profile cams are available and affordable, getting 300whp should be easy.

I hope this write-up helps, and shows that clearly the stock intake manifold is restrictive.

Rahim

 

[Greg Z]

Good job Rahim. i will be needing one of those. How much? Prolly will be able to do before/after on a FI car if all works out.

 

[FastraxTurbo]

Overlay your previous dyno with the new one. The two you posted are using different correction factors.

 

[RagingAngel]

bump from the half-dead.

With this porting mod, has anybody done before and after AFR readings with a wideband?

Some of the losses shown http://www.fastraxturbo.net/NSX/NSXmanDyno.jpg
could actually be due to lean spots down low.

Unless I'm wrong, I don't think any of the NSXs run MAF with the ability to self-adjust/correct for increased air flow.

 

[L_RAO]

Bump from the (kinda) dead.

Were any other experiments conducted?

 

[96cxt]

No, not on my end. Not much else there to experiment with.

 

[L_RAO]

I've always wondered why the opening where the TB meets the manifold is offset, thus limiting one's ability to effectively run a bigger TB since port matching would be limited.

Was there some sort of consideration for space for other parts (sensors, hoses, etc.)? Or is there another reason?

 

[Nero Tenebre]

Bumping this thread up, Rahim's dyno looks like it didn't affect low end torque much at all to delete the VVIS completely. I saw another dyno sheet that did clearly show low-end torque loss by deleting the plate. Seems the consensus is that it's a given to do that for FI applications so I'm gonna do the same. But another thing, it may still be a good idea to do this if you are staying NA too... when they took my manifold apart they found one of the butterfly valves disconnected because the screws worked loose. EXTREMELY LUCKY FOR ME, since I could have been this guy: http://www.nsxprime.com/forum/showthread.php?t=155613&highlight=intake+manifold+bolts+loose

Thankfully I decided to have it all taken apart and cleaned when I did, I cringe to think what could have been. They put locktite on all of them now but I'm gonna delete it. I guess it may cost a decent amount of torque throughout the lower rev range but I plan to go FI so it will be a restriction then.

Part of this thread should probably go in the new NA forum..

 

[greenberet]

Compare Rahim’s "after" dyno plot to this:

With the VVIS in place you have a torque hump between 3000 and 5000 rpm. Rahim’s "after" plot doesn’t.

Rahim wrote that the dyno plots he posted above were before and after he installed his cold air intake. So I assume the "before" plot is with the VVIS and the OEM intake in place and the "after" plot is without the VVIS but with his new cold air intake system mounted. If that's the case, it's hard to determine what impact simply deleting the VVIS had. Also, FastraxTurbo’s point is worth considering – the "before" and "after" plots may have been corrected differently, making it hard to compare the absolute numbers generated.

 

[A.S. Motorsport]

Thanks everyone.

Hugh I already Pm'ed you.

David, I'm working on the internal TB plate. I dropped one of to the machine shop to get it machined/gutted so it will only be a spacer. But I'm gonna try to take it one step further. I want to dyno all 3 ways.

1) With the ITB (stock) in place

2) With the ITB (machined/gutted) in place.

3) Completely omiting the plated making the manifold shorter so there would be less volume to fill in the manifold.

If anyone has already tried this please chime in.

Thanks
Rahim

For most stock/na cars it's better to leave them in place as they help in generating torque in low RPM region.
Gutting them will give you a bit more plenum volume but loose you torque it isn't worth on a NA car unless it's highly modified or running boost.

You'll notice it in driving.

EDIT:
I just read the rest.
These is exactly what i was talking about,
C32A and C35A become unbearable if you remove there three stage VISS.

 

[A.S. Motorsport]

On a other note,
For the larger displacement of higher lift cars there are other options as well.
Increasing plenum by way of a manifold spacer although you can't lower the bottom plate further in a C engine.
Enlarging the VISS system with bigger butterfly's although if enough displacement is reached the system becomes irrelevant due to the increased low end torque due to displacement.

Increasing plenum on the TB side, this works on C32A and C35A engines i make spacers for those and everyone is pretty happy with the result those spacers start to work when VISS becomes active in stage 3 (3300+ on the SOHC engines)

I've to find some time to do more testing on those spacers and dyno runs.