TDi Dyno Day Results thread :)

[AR]

Around 5 bhp extra.

I still don't get why you guys did not go for test pipes.

[markc]

Around 5 bhp extra.

That would be nice

I still don't get why you guys did not go for test pipes.

I'm thinking they'd be A) too noisy and B) on our OBDII cars the "bodge" of locating the post cat sensor/s in extended fittings is hit and miss to say the least.

Cheers

Mark

[AR]

That would be nice



I'm thinking they'd be A) too noisy and B) on our OBDII cars the "bodge" of locating the post cat sensor/s in extended fittings is hit and miss to say the least.

Cheers

Mark

Mark I had them on a 3.2 before and no problem there, most exhaust shops can build you an extended bung. You can also have a pair of resonators built instead of the straight pipe design.

[markc]

Mark I had them on a 3.2 before and no problem there, most exhaust shops can build you an extended bung. You can also have a pair of resonators built instead of the straight pipe design.

Well they may "work", some or most of the time, but you have to admit it is a bodge. By work I mean prevent a CEL (Check Engine Light) being triggered.

The second sensor is there to both determine that the CAT is working AND work with the first one, via the ECU, to ensure that the fuel/air ratio is correct. I wouldn't want to risk running too long with potentially incorrect fueling.

Even if the the sensor relocation does work and you run de-cat (test) pipes you may well fail your MOT emissions test and therefore have the hassle of swapping back to standard cats every year. Too much hassle for me.

Cheers

Mark

[Senninha]

The second sensor is there to both determine that the CAT is working AND work with the first one, via the ECU, to ensure that the fuel/air ratio is correct. I wouldn't want to risk running too long with potentially incorrect fueling.

Even if the the sensor relocation does work and you run de-cat (test) pipes you may well fail your MOT emissions test and therefore have the hassle of swapping back to standard cats every year. Too much hassle for me.

Cheers

Mark

This is exactly why I have opted for high flo CAT's over test pipes, as well as not wanting to be too loud. I much prefer the ability to cruise into town un-announced and keep the loud bit for when I want to play

[NoelWatson]

Talking of cats, was looking at resetting ECU, and found this

http://itisfresh.com/how-to-reset-ecu-acura-nsx.html

"or you may decide to erase the catalytic converters (obviously for track use) and the car bogs down.. "

Mine felt like it was bogging down so have just done this

[drplc3]

Hi Luke, the Type S myth is busted, Paul's car (Senninha) pipped mine and the other Paul (NSX200) was real close. Both, as well as me, have non factory exhausts. Look at Leigh's (Kowalski) numbers for what a 3.0Ltr car is capable of with exhaust mods, just make sure you have your fingers in your ears

A top event and some properly useful data and comparisons have been recorded.

The guys at TDI really know their stuff! Project "airbox" starts now...

Very interesting chat with Sam of TDI as to how to overcome the air/fuel mix issues to release those extra ponnies. I'll email SOS and ask the question re throttle bodies and update if I get any answers

[markc]

Very interesting chat with Sam of TDI as to how to overcome the air/fuel mix issues to release those extra ponnies. I'll email SOS and ask the question re throttle bodies and update if I get any answers

I've spoken with a couple of knowledgeable and well respected sources about this.

The consensus is that the 3.0Ltr cars will not benefit from a bigger throttle body even if the more usual I/H/E upgrades have been done. It won't hurt but it won't help.

It will however benefit 3.2Ltr cars as they have slightly better breathing (bigger valves) and the cross sectional area of the standard throttle body does "strangle" the motor a touch. There is science behind this which I don't have to hand but someone else might chip in with that

Science of Speed will claim a few hp's for mechanical standard 3.0 and 3.2Ltr cars but in truth it really only comes into it's own for FI and their increased capacity (3.3/3.6/3.8Ltr) NA builds.

I plan to get me one at some point anyway

Cheers

Mark

[greenberet]

I'll email SOS and ask the question re throttle bodies and update if I get any answers

In theory, the intake tract of a naturally aspirated engine should be shaped kind of like a funnel, slowly getting wider the further you get away from the cylinder head.

If my measurements are correct, a stock NSX’s intake tract has the following cross sections:

• Intake opening in cylinder head: 18.0 cm2. This is also the cross section of the exits of the individual runners in the intake manifold.
• Intake manifold entrance: 34.2 cm2. In our six-cylinder four stroke engine, 1.5 cylinders will always be inhaling at once, so you’d want the intake manifold entrance to be somewhat more than 1.5 times as large as the intake openings in the cylinder head. Our manifold fits the bill nicely with an entrance 26.6% larger than 1.5 times the cross section of the openings in the cylinder heads.
• Throttle body outlet: 32.2 cm2. A tad smaller than the entrance to the intake manifold, if my measurements are correct, so not quite ideal.
• Throttle plate: 29.6 cm2 effective cross section. Narrower again and now only 9.7% larger than 1.5 times the intake openings in the cylinder heads. How much of a restriction this poses will depend on the flow rate through the throttle body. According to informed sources, it does not cause a noticeable restriction with stock or lightly modified NA1 engines. With heavily modified NA1 engines and stock NA2 engines, it does.
• Airbox exit: 59.1 cm2. Much, much larger than the cross section of the things downstream of it so this shouldn’t pose any restriction.
• Air filter: 496.9 cm2. Not even accounting for the pleats. How much or even whether an aftermarket filter is really less restrictive than the OEM filter is open for contention. I would love to see some dedicated pressure drop measurements carried out in an NSX. The measurements taken during the 2009 TDi dyno day indicated no difference in pressure drop between the cars with OEM vs. aftermarket airboxes/air filters.
• Exit of OEM intake snorkel: 65.1 cm2. Larger than the exit of the airbox, so the funnel analogy holds and this shouldn’t be a restriction, either.
• Main opening of intake snorkel: 50.6 cm2. In stock form, this is the only entrance used. It’s still 47.9% larger than the entrance of the intake manifold, so it may not pose much of a restriction. In this configuration however, the funnel analogy doesn’t hold.
• Resonator opening in intake snorkel: 19.6 cm2. Getting rid of the resonator will increase intake noise and the two openings in the intake snorkel together have a larger cross section than the exit. In this configuration, the stock intake snorkel doesn’t look like it would be a bottleneck either.

How generous the radii in the intake system are impact its efficiency as do its resonant frequencies (which the VVIS helps out with). Just looking at the cross sections, though, the following two modifications seem logical in an otherwise stock intake system:

1. Get rid of the resonator in the OEM intake snorkel, replacing it with a bellmouth, if possible.
2. Get the stock throttle body bored out so that the effective cross section at the throttle plate is no longer smaller than the entrance to the intake manifold and have the exit of the throttle body port matched to the stock intake manifold. I spoke with Chris at Science of Speed and their big bore throttle body porting service does both of these things. Edit: SoS increase the size of the throttle plate from 65.5 mm to 70.5 mm. Subtracting the height of the spindle, this increases the effective cross section to 34.7 cm2. They bore the exit of the throttle body out to 66mm, port matching it to the intake manifold.

With those two modifications, an NSX’s intake looks like a well balanced system without obvious bottlenecks. Further changes will probably have a noticeable impact on horsepower only if you modify the intake system along its entire length, starting at the cylinder heads. New airboxes and intake snorkels can make the engine sound more powerful, though!

[markc]

That'll be the science bit I was referring to, thanks Andreas

Cheers

Mark