90deg downwards intake trumpets 90deg intake upwards 90deg upwards

It's Dyno time

As I write this it is nearly Christmas and Santa has brought me a great present in the form of a Superflow 902 engine dynamometer. We have installed a test engine just to experiment a bit and get to know how it all works. The software is very different from the TAT kit we use on the rolling road and I have had to go back to school to pick it all up.

I have to confess it felt a bit strange sitting at the consul and feeling totally clueless, even a bit confused. I have been operating the rolling road for over 17 years now and I do it without thinking about anything other than what I am trying to achieve. With the Dyno I had to search around the screens to see what’s located where. I have to say that on the first power run I was more than a little nervous.

At first I was a bit disappointed because I was getting different results depending on how I tested the engine. But I had a word with Aaron Tucker at H.T. Racing - who has run a Superflow for a number of years and Aaron said that this was correct because you will get a different result on a step test compared to an acceleration run. The norm is to accelerate at 200 rpm/sec and log in set rpm steps, rather than try and log every point that the software is capable of logging. A run on the 2.3 Duratec mule engine took about 20 seconds which relates very closely to the rolling road power run. That has now become my standard with logging in 250 rpm steps.

I mapped the engine on steady-state running and it was just so easy. The drive-by-wire set up we have puts the load dead centre, then you release the throttle brake, dial in the rpm and the 902 does the rest. The stock engine makes 143 bhp at 5750 rpm and 154 ft lbs of torque at 4250 rpm. With Jenvey 45m bodies, my adjustable intakes and a Westfield 4-2-1 exhaust we recorded 170 bhp and over 180 ft lbs of torque.

Having started to get the hang of things I looked about for something to test. I have had a lot of enquires about inlet lengths since developing the ALI (Adjustable Length Inlet) but I did not want to go over old ground so I came up with another test. People keep asking me if a curved intake loses power and I have always said that I did not think it would lose much, if anything at all. So, there’s only one way to be sure.

I bought in four 90 degree silicon bends and cut up some of our intake trumpets. I tried to get the lengths the same for the straight intakes and the 90 degree ones but I may have been a few millimetres out. I took three “pulls” (see how quickly I am learning the Dyno tuning lingo) with the straight trumpets and then used the software to draw an average curve. Next I made up the curved intakes and the first run looked pretty much like the straight ones. The next two however seemed a little down. Not to worry, I can average out the results for consistency.

At that point young John came in and asked why I was running the engine with one bell-mouth missing! Being a cheapskate I just pushed the bell into the rubber hose and left off the clips. I was trying to save the cost of four cable ties...

Straight Vs Curved trumpet dyno test

We found the bell on the floor and four cable ties later I repeated the test and averaged out the results. At first sight the curved intakes looked to have lost power, but when you look at the scale the difference was tiny, just a couple of bhp at peak. Okay, it’s still a loss but it’s very small and interestingly right across the rev range. This is not an air flow issue; you can see how that looks on the Fiesta test elsewhere in these pages. I believe it is the curve taking the edge off the intake pulse and so marginally reducing the effect. If I had done these tests on a rolling road I would probably now be telling you that it makes no difference but the Superflow looks like it is going to be deadly in finding small differences. More dyno fun next issue!

Fiesta Fun


This is the engine that we did all the original testing on for the adjustable inlet system. The engine is now installed in a newer Fiesta and fitted with our Pipercross foam filters. Just to make sure everything was still sound we ran it up on the rolling road. The install wasn’t quite allowing full throttle but we still had 178 bhp. This is only a few bhp down on the original test. However, looking at the bonnet it was obvious that this would sit on top of the filter the way we had everything positioned. For that reason we shut the lid and did another power run.

You can see that up to 5,500 rpm there was nothing in it, but at peak torque the restricted filters started to hold the engine back. We lost 5 bhp at peak – just by closing the bonnet. This is not the first time I have seen this. We had a TVR some year’s back that dropped 20 bhp with the bonnet shut. It pays not to get too carried away when mapping and to do a final power run with the bonnet shut if it looks like getting in the way of the air flow.

K Series Capers

David Harvey's graph
Lotus 340R airbox test

David Harvey’s 340R is a regular here at Emerald and David has tested more K Series engine configurations than you can shake a stick at. He currently runs a self-built 2.0 litre engine. This is a serious piece of kit and we recently did some testing on inlet lengths and shapes. Dave ended up with his chosen trumpet and air box configuration which gave him the torque in the right place (for a race car) and 248 bhp at peak power.

What’s really interesting is that if you take the air box off and record a power run the engine drops power everywhere and doesn’t want to run past 6,500rpm. Peak is normally up at 8,250 rpm. The air box is essential to make the engine work. We have done a lot of work on a Datsun 240Z that does the same airbox trick, but that one drops nearer 30bhp. This is yet another area for dyno investigation but that can wait until I have had a play with a few other things.

Lotus 340R no air box