TDi Dyno Day Results thread :)

[kowalski]

Yep mine even surprised me!

Looks like I will have to go the same route as Paul with the throttle body as well, and also mine had problems running way to lean.

Interesting thing was that both the 91, 3.0 revved to 8200 whilst the other 94/95 3.0, limited at 7800.

Was nice to hear mine from outside as well, didnt realise it was that loud lol

leigh

[forumadmin]

What's this talk of throttle bodies all about?

No photos? Sounds like a good day, by people that know what they are talking about.

[BabyG]

Rich/ Baby G
1991 manual, standard spec

Max Power 241.2 @ 7390rpm
Max Torque 184.0 @ 6460rpm

Happy with that - I don't think the old girl's lost a single pony in 17 years!


Echoing earlier comments, big respect to what the guys at TDI know about this stuff - they know their engines! And, as it turns out, their brakes - watch this space ahead of the 'Ring in August...

[Senninha]

What's this talk of throttle bodies all about?

No photos? Sounds like a good day, by people that know what they are talking about.

I'm sure someone with greater technical knowledge will chip in here, but in basic terms, the guys at TDI were suggesting that whilst the larger airbox some of had fitted seems to be working ok, there is a restriction somewhere in the system that is causing a drop in pressure. This resulting drop in pressure is causing us to drop torque and therefore bhp. One theory is that it may be at the throttle bodies where this occurs.

If you look at the SOS larger bore TB, it has a larger and smoother intake area that in theory would reduce this restriction. The question I have put to SOS is simple. Have they developed this because of a genuine need, ie they have the same restriction problems we identified yesterday, or have the made them just because people asked them too.

The only other potential area for a small gain might be the cats. Interestingly Leigh runs without cats and showed great results. Honda cats are not usually over restrictive, but TDI suggested that if like me, you dont want to progress onto changing cams or other engine components, then to complete the 'external' upgrades this could be a consideration.

Hope this is clear

regards, Paul

PS - no photos because it was pi****g down ... and today it is snowing!

[britlude]

a pic of the setup.....



i have a couple of pulls on vid is someone has somewhere to host them! must sort that out at some point!

[forumadmin]

I'm sure someone with greater technical knowledge will chip in here, but in basic terms, the guys at TDI were suggesting that whilst the larger airbox some of had fitted seems to be working ok, there is a restriction somewhere in the system that is causing a drop in pressure. This resulting drop in pressure is causing us to drop torque and therefore bhp. One theory is that it may be at the throttle bodies where this occurs.

If you look at the SOS larger bore TB, it has a larger and smoother intake area that in theory would reduce this restriction. The question I have put to SOS is simple. Have they developed this because of a genuine need, ie they have the same restriction problems we identified yesterday, or have the made them just because people asked them too.

The only other potential area for a small gain might be the cats. Interestingly Leigh runs without cats and showed great results. Honda cats are not usually over restrictive, but TDI suggested that if like me, you dont want to progress onto changing cams or other engine components, then to complete the 'external' upgrades this could be a consideration.

Hope this is clear

regards, Paul

PS - no photos because it was pi****g down ... and today it is snowing!

Did they take some kind of measurement for this, or was it down to experience? The thing is, where does it stop? If you do something to the throttle there will be a bottleneck somewhere else. There always will be.

It's snowing here too, but at least I can make use of it!

[markc]

Here's mysunderstanding of the science Kevin...

The TDI/Rototest setup monitored inlet pressure at 2 points. They tee'd into the inlet manifold side using one of the grey pipe/tubes top of the engine and also stick a sensor up into the passenger side inlet grill. They therefore measure airpressure at either side of the throttle body. The reasoning for sighting inlet restriction being a problem is that during the "pull" air pressure between these 2 points drops.

The chap described it as an air density problem. Being essentially an air pump, the engine will pump 3.2 litres of air (in my case) with each revolution regardless of air being available with restricted flow or not. However, with a perfect air mass and no resitriction the density (charge) of that 3.2 litres of air will be higher. Increased air "charge" directly increases torque produced, and because torque and power have a fixed relationship (bhp=(torque x revs) /5252), are directly related to power.

Look at my parameter plots attached...

The blue line (the one starting 2nd from top on the left side) is InletPressure, it's axis is Y4 and the scale 0.95 to 1.050 bar. On the left side of the graph it starts at base atmospheric pressure, 1.011 bar in my case. As the rev rise though the "pull" pressure steadily drops. In a perfect system it would be a flat line.

The early runs, Noel's and Mark's for sure, used a differant scale so their plots won't be of any use but did anyone who attended get a flatter InletPressure plot??

I have a standard airbox and filter and the guys with Procar airboxes fared no better. We therefore suspect the probelm is elsewhere. The Procar airbox may be better than the stock one but if it is it's being strangled by something else. The most obvious thing is the throttle body hence Paul's question to SOS.

This could of course be a misleading result and taking us down a blind alley BUT there could be some more relatively low cost power to be had here

Cheers

Mark

[simonprelude]

The main issue that has been found with a lot of Honda systems firstly points to the TB, however when that has been opened up, either fully or venturi you then come across the restrictions in the intake manifold. Then dig deep

[NSX 2000]

2005 3.2 Manual Coupe
bhp related mods - Titec exhaust + Procar airbox
max power 267 bhp @ 7300 rpm
max torque 205 lb-ft @ 6440 rpm

Is it also worth our while to send the same email to detlef and ask what his dyno results had shown with regards to his airbox?

The only thing with a dyno test is the car is static; would you get a different result if moving? When I've spoken to engineers who prepare race cars they will spend weeks at the factory playing with the engine, then when they get to the track they start getting completely different results, iirc this is most evident in WRC cars.

I wonder if we move away from dyno and see what happens in a straight line at something like V max. Would the people with more HP be able to beat Noel's top speed?

Just to pee on Paul's parade I think he only got best HP due to the fact that the air was at its lowest temperature when he had his test

Paul.

[NoelWatson]

I have a theory that the 2000 exhaust changes were detrimental to the 3.2's power output.