Another minor update.
I have got hold of a bored out throttle body and am ready to fit the mildly ported banana manifold to an engine and do some before and after testing.
A bit about the test car - my grandpa spec VT Calais which happily sits in the shed with a flat battery. It’s an April 99 model so towards the last of the 5.0s. I would have been lucky to do 2000 kms in it since I bought it a few years back which is another reason I am not so keen on adding another 1200kms just for some dyno testing. It does have a few miles on it already but is close to immaculate with leather interior, beautiful to drive and is pretty much stock other than a set of R8 rims and a dual 2.25” XForce catback that I fitted not long after I got it.
I did have hopes that my eldest daughter would use it for her formal car when she finishes school, but there’s a big block HQ 2 door Monaro that she thinks will be a better option. I think she would rather walk than be seen in the Calais which might as well be a beige Camry as far as she is concerned. Luckily I have a couple of nephews with good taste who are keen to inherit it one day.
- Calais.JPG (134.03 KiB) Viewed 1997 times
Regardless, this Calais can actually be pretty good on fuel on the highway, and the best I have seen on the trip computer was 8.0 litres/100km. It has a nice exhaust note and is not too loud, and is really comfortable. It has the factory 179 kw roller cam, stock Bosch 973 injectors, stock exhaust manifolds and cats. Diff gears and transmission are stock. As far as I know, it has never had the heads off, but the intake manifold has been changed at some stage as it has an earlier manifold on it with a bung in the MAT port. No idea why and all I can think of is they must have swapped it doing the valley gaskets years back. Either that or the original one was porous in some way. Interestingly this Calais has the HSV CNPK memcal from the factory. Matters not. Springs, struts and shocks are all original, not that wheel spin or getting off the line is going to be a problem.
But while it is nice to drive, it is absolutely gutless. So another reason why it’s not the best candidate for testing a ported manifold but it’s what I have. It’s a shame really as a dyno test on this would have been good for a laugh.
I guess some will say the 2.25” exhaust would be limiting the hp and any normal person would have gone the dual 2.5” or dual 3”, but my personal opinion is that the smaller pipes sound better. Power wasn’t a consideration as this thing is lucky to hit 3000 rpm when I do drive it so dual 2.25” pipes are more than enough coasting around town or along the highway.
I have ordered an NVRAM loaded with the enhanced bin, and have fitted this with the revised table to the Default Air Flow vs TPS so the transmission doesn’t play up with the bigger throttle. But the fuel and ignition tables etc are all stock.
To date, I have done 4 runs on the same stretch of road with the stock manifold and throttle body, and repeated this again with the 70mm throttle body.
What I found is possibly what everyone else already knew - that there is only a small gain fitting a 70mm throttle over the stock 65mm. But to be fair though it was a much hotter ambient on the night I tested the 70mm throttle, and the trans slip on the gear changes seemed a little worse. Maybe if the ambient temp was the same for both tests, the 70mm throttle would look a bit better.
The main thing that I noticed with the 70mm throttle is that it sticks open and didn’t want to close. With the engine stopped, it’s completely fine, opens and fully returns to a close and repeats this every time. But start the engine and it just doesn’t want to return home to fully closed. Almost as if engine vacuum is holding it open. I have heard of issues with these bored throttles sticking, but always thought it was due to a problem in the throttle shaft but that’s not the case here. I’ll sure smarter blokes than me have looked at this but I managed to get it working fine by cranking up the spring tension on it a little.
But at the moment, the improvement from a 70mm throttle isn’t enough that I would keep it on there – not on a stock Calais anyway. If it was a manual, then possibly worth the effort.
This is it fitted with 70mm throttle. In the photo you can see where I have moved the spring around to the next position to get it to return.
Next step is to fit the mildly ported manifold and get some more times with both the stock 65mm and 70mm throttle body. I have made a start already and have the coolant out ready to attack it. Will replace all the heater hoses while I am at it and obviously give it an oil change.
To be honest I was expecting a better result from the bored out throttle body. So now I have a bad feeling that based on what I have seen so far that getting some 0 to 100km times won't prove anything – which is probably again what everyone else already knows. Maybe a bit more cam and compression might be a different story, but I’m thinking it’s pretty unlikely that a ported manifold on a stock 5.0 will show any gains at the same rpms as an unported one. So unless you wring its neck a little more with some higher rpms, you won’t see any gains in 0 to 100km/hr times whereas a dyno would probably show this.
Anyway, I will press on as I have no other options. Good or bad, faster or slower will post up what I find.
But this is the results so far.
- Recorded Times.JPG (32.59 KiB) Viewed 1997 times