Vixen 302 V8 Tweety
Discussion
Hi Neil, the numbers mentioned are at the flywheel. And yes, I promised to address the airbox question. After talking to the experienced people at KMS, they agreed with the general principle of the current airbox, so front intake (unless I wanted to cut the bonnet and fit a scoop ala AC Cobra). But unfortunately the new ITB set up means the current airbox cannot be used anymore. Full radius trumpets: yes, done. They stressed that for these types of engines, the best thing to do is to increase the inlet lengths as much as possible, preferably to more than 300mm (see e.g. BMW M5). This means in my installation a 90 degree bend per runner and using two side mounted airboxes, similar to a V8 Cerbera. So my plan is to experiment with that in the future.
Edited by ephemera on Thursday 8th November 07:05
Hi guys, thanks for all your replies!
@GT Rene: yes the infamous Lucas 7" inch lights are OK-ish but modern lights have indeed improved a lot. For the moment it is OK but I notice that people hear the car before they see it haha ;-) Mass of the car by the way can be seen earlier in this thread, 893.5 kg wet.
@SRT Hellcat: well spotted, this was also the first thing I asked when I saw the dyno chart. Explanation is that the "wheel" numbers are actually the numbers at the measurement location at the shaft of the rollers, and include the dyno losses itself, the tyre slip and the roller's inertia. So it is not the value at the contact area between wheels and rollers. It would have been clearer if they left that line out or renamed it. My estimate for this car is that the actual wheel power is indeed approx. 50-60 bhp lower than the flywheel power mentioned. Wow, and what a great project you must have, very interested!!
@Spitfire4V8: honestly very honoured that you joined this thread, very impressed with all your work. What a coincidence and a nice read on your experiments on induction lengths. I feel technically and morally obliged to investigate this in more detail on my car, the possible benefits and changes are very significant and interesting! Two questions if I may, would using one airbox per cylinder bank like the AJP Cerbera be also OK for a crossplane V8? And would a tight 90 degree turn just above the ITB's be a big problem (in order to package the say 300 mm induction length)? I am thinking of either aluminium tubing or silicone hoses to use for the experiment.
And still thinking there should be a market for a robust aftermarket variable length intake system with an actuator...
@GT Rene: yes the infamous Lucas 7" inch lights are OK-ish but modern lights have indeed improved a lot. For the moment it is OK but I notice that people hear the car before they see it haha ;-) Mass of the car by the way can be seen earlier in this thread, 893.5 kg wet.
@SRT Hellcat: well spotted, this was also the first thing I asked when I saw the dyno chart. Explanation is that the "wheel" numbers are actually the numbers at the measurement location at the shaft of the rollers, and include the dyno losses itself, the tyre slip and the roller's inertia. So it is not the value at the contact area between wheels and rollers. It would have been clearer if they left that line out or renamed it. My estimate for this car is that the actual wheel power is indeed approx. 50-60 bhp lower than the flywheel power mentioned. Wow, and what a great project you must have, very interested!!
@Spitfire4V8: honestly very honoured that you joined this thread, very impressed with all your work. What a coincidence and a nice read on your experiments on induction lengths. I feel technically and morally obliged to investigate this in more detail on my car, the possible benefits and changes are very significant and interesting! Two questions if I may, would using one airbox per cylinder bank like the AJP Cerbera be also OK for a crossplane V8? And would a tight 90 degree turn just above the ITB's be a big problem (in order to package the say 300 mm induction length)? I am thinking of either aluminium tubing or silicone hoses to use for the experiment.
And still thinking there should be a market for a robust aftermarket variable length intake system with an actuator...
Edited by ephemera on Sunday 11th November 22:34
Hi all,
Here the promised update from my side regarding the dyno testing with various inlet lengths.
As predicted by the experts some very interesting results.
Of course there is always a time limitation on everything you want to test but here the summary, for who is interested:
Boundary conditions:
Vixen V8 302 on ITB's strapped to the dyno (another dyno than last time), but it turned out that at rpm's higher than 4500 rpm there was just too much slip to perform reliable tests in that rpm area. But I was mainly interested in the real world range.
To check the consistency between the first dyno and this one, a reference test was carried out, and indeed, until 5000 rpm very identical torque and power curves (now with 30 mm trumpets, former one with 45 mm trumpets). So the old values are OK as a base line (356 hp at 5880 rpm, 450 Nm at 4860 rpm, and a fairly flat torque plateau between 4200 and 5500 rpm).
ITB's with only 30mm trumpets: 333 hp at 5200 rpm, and rising, but at higher rpm no reliable test data. Torque 460 Nm at 4015 rpm.
Then I attached 90 degree copper knees, 50mm diameter on the ITB's (with copper welded (!) flanges), and attached to them an additional 150mm hose per cylinder with trumpets at the ends, no airboxes. The results?
328 hp at 5139 rpm (and rising), 500 Nm at 3931 rpm
Between 3000 and 4000 rpm on average 30 Nm more than when only using trumpets.
Then the 90 degrees knees with 700mm hose with trumpets on their ends, no airboxes. The results?
315 hp at 5290 rpm, and rising, and 493 Nm at 3867 rpm
But... between 2200 and 3300 rpm even more torque than in the last situation, with a max increase seen of again 30 Nm at 2800 rpm. And until 4200 rpm as good as no deterioration in torque compared to the last situation.
Then just for science sake, only the 90 degree knees, no hose, no trumpets:
318 hp at 5225 rpm, 474 Nm at 4711 rpm. More peaky torque line.
(And so either the trumpets didn't make that much of a difference, or the extra length of the knees compensate for not mounting the trumpets).
Unfortunately no easy to read graphs available, but I included some indicative photo's anyway.
Conclusions:
Yes it is true that with only playing with the inlet lengths an impressive change can be accomplished. If you have the engine bay room available, some hose can gain 10% in my case over a very large rpm range without sacrificing too much in other areas, if at all.
90 degree knees with large diameter do not really restrict flow.
Trumpets don't give an enormous difference in my case.
I wished I had time to conduct more and better tests (airboxes etc) but that's life. I am happy with the results, and am thinking what I would like to install as the next step.
O yes, for the various runs, the mapping was adapted to keep the lambda ideal.
This year's intention is to go out as much as possible out on the road and enjoy it!
Here the promised update from my side regarding the dyno testing with various inlet lengths.
As predicted by the experts some very interesting results.
Of course there is always a time limitation on everything you want to test but here the summary, for who is interested:
Boundary conditions:
Vixen V8 302 on ITB's strapped to the dyno (another dyno than last time), but it turned out that at rpm's higher than 4500 rpm there was just too much slip to perform reliable tests in that rpm area. But I was mainly interested in the real world range.
To check the consistency between the first dyno and this one, a reference test was carried out, and indeed, until 5000 rpm very identical torque and power curves (now with 30 mm trumpets, former one with 45 mm trumpets). So the old values are OK as a base line (356 hp at 5880 rpm, 450 Nm at 4860 rpm, and a fairly flat torque plateau between 4200 and 5500 rpm).
ITB's with only 30mm trumpets: 333 hp at 5200 rpm, and rising, but at higher rpm no reliable test data. Torque 460 Nm at 4015 rpm.
Then I attached 90 degree copper knees, 50mm diameter on the ITB's (with copper welded (!) flanges), and attached to them an additional 150mm hose per cylinder with trumpets at the ends, no airboxes. The results?
328 hp at 5139 rpm (and rising), 500 Nm at 3931 rpm
Between 3000 and 4000 rpm on average 30 Nm more than when only using trumpets.
Then the 90 degrees knees with 700mm hose with trumpets on their ends, no airboxes. The results?
315 hp at 5290 rpm, and rising, and 493 Nm at 3867 rpm
But... between 2200 and 3300 rpm even more torque than in the last situation, with a max increase seen of again 30 Nm at 2800 rpm. And until 4200 rpm as good as no deterioration in torque compared to the last situation.
Then just for science sake, only the 90 degree knees, no hose, no trumpets:
318 hp at 5225 rpm, 474 Nm at 4711 rpm. More peaky torque line.
(And so either the trumpets didn't make that much of a difference, or the extra length of the knees compensate for not mounting the trumpets).
Unfortunately no easy to read graphs available, but I included some indicative photo's anyway.
Conclusions:
Yes it is true that with only playing with the inlet lengths an impressive change can be accomplished. If you have the engine bay room available, some hose can gain 10% in my case over a very large rpm range without sacrificing too much in other areas, if at all.
90 degree knees with large diameter do not really restrict flow.
Trumpets don't give an enormous difference in my case.
I wished I had time to conduct more and better tests (airboxes etc) but that's life. I am happy with the results, and am thinking what I would like to install as the next step.
O yes, for the various runs, the mapping was adapted to keep the lambda ideal.
This year's intention is to go out as much as possible out on the road and enjoy it!
Edited by ephemera on Sunday 31st March 00:07
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The rear end is a Viper LSD with Viper driveshafts going into custom alloy fabricated uprights.
If I would use the trumpets only, I will use the old type of Lexan airbox, but lower, two air hoses to the front, and two conical air filters each side of the radiator.
If I will use the long inlet system, I can either make two airboxes and use the same air hoses to the front, or alternatively get air in from the side vents using a panel filter.
And the simplest but least favourable option in my opinion is to use two long foam elements over the trumpets.
If I would use the trumpets only, I will use the old type of Lexan airbox, but lower, two air hoses to the front, and two conical air filters each side of the radiator.
If I will use the long inlet system, I can either make two airboxes and use the same air hoses to the front, or alternatively get air in from the side vents using a panel filter.
And the simplest but least favourable option in my opinion is to use two long foam elements over the trumpets.
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