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AutoSpeed Interview: John Sidney of John Sidney Racing

Intake trumpet designs, rod lengths, heads, engine computer simulation programs - a mass of interesting stuff!

by Julian Edgar

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Melbourne's John Sidney Racing is a workshop boasting a wonderful range of racecars, mostly with big engine V8 power - SuperCars, Nascars, Auscars. With a very well equipped engine dyno and a long history of top motorsport preparation, JSR is a place where you take note of everything that's casually said. We spent an enjoyable few hours covering a range of subjects, most of which were about power...

We started off by examining a 5 litre Ford V8 that JSR is developing for Australian SuperCars. As with all of these engines, it uses a crossover inlet manifold with long, straight trumpets, the injectors suspended above the open bellmouths.

AutoSpeed: Takes us on a tour of the engine!

John Sidney: We've made four ram-tube combinations - different lengths, different tapers - that we will be trying (on the engine dyno) ...

AutoSpeed: Let's stop on the ram tubes. In the car there's an airbox that goes on top of the belmouths. When you have an enclosed plenum chamber on top of the engine, do you find that that affects the resonant tuning of the intake system to a large degree?

John Sidney: Yes, slightly. It affects it only if you have bad air in the dyno room. If you have good, fresh, clean air it doesn't affect it.

AutoSpeed: So it doesn't change the tuning?

John Sidney: You put the airbox on in the dyno room and it'll probably knock one percent out of it, but if the air in the dyno room is contaminated by the exhaust and (high) temperature, of course it really knocks things around badly. If the air duct is coming in the top and the fresh air is reaching those ram tubes, then we've got a pretty perfect world. We put an airbox on and then we bring the air in at the front of the airbox, it's basically receiving the same air. Usually if we put an airbox on one of these engines and then put it in the car, the change in fuel trim required in the car is very minute. Very minute.

AutoSpeed: So the pressure build-up at speed isn't enough to affect the tune?

John Sidney: No, not really. We're still a little bit lost over that because we can see a pressure build-up of seven to eight inches of water and it's not requiring much fuel trimming in the car at all. Yet, some engines do need it....

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AutoSpeed: How do the trumpets that you are trying vary from one another?

John Sidney: The tapers inside the tubes are different, the radius of the bellmouth is different, the lengths - we might use these this short and then we've got more that are longer. These are about six inches, and we go up to eight and a half inches. We also have different types of material - carbon fibre and spun aluminium.

AutoSpeed: Why would the material make any difference?

John Sidney: The carbon fibre keeps them cooler, while the aluminium attracts the temperature - heats the air up and then of course things go badly. We've got three different tapers that we're going to use and we have four different lengths - it's taken weeks to do it all because every time that we shorten the tubes, we have to move the injectors with them!

AutoSpeed: With the different designs of trumpets - is it basically let's just try some and see what happens?

John Sidney: We'll use a wide taper like this with a long tube for two different reasons: to try to trap more air with the wide taper and then long in length to get some airspeed down low. Or, we'll use a long skinny one that we know is too long - the bottom end is awesome because the airspeed's there - and then we'll progressively shorten it down until we can get maybe the ultimate effective length.

AutoSpeed: And do you lose top end with the very long trumpet because of the pressure drop through the length of the trumpet?

John Sidney: Yes it's the surface area.

AutoSpeed: The throttle bodies - are you trying different ones of those?

John Sidney: No, we're not sure about those. We're using our standard spec (multiple butterfly type) and when this is all over, if we haven't gone far enough we will take these and bore them out - and then we'll have to start again with the trumpets!

AutoSpeed: And you'd be assessing whether these were big enough by looking at the MAP pressure inside the actual manifold?

John Sidney: No, we'd just be looking at the fuel numbers in relation to horsepower. If it's making 650 horsepower we'll be happy; if it's making 620 - and the fuel numbers are still down around what we call 100 - we'll have to re-think.

AutoSpeed: In normal road car engines - which I'm more familiar with - tumble and swirl going into the combustion chamber are vital for emissions performance and other sorts of performance. Is that the case with race engine like this?

John Sidney: No. We don't want any tumble - because tumble is slowdown; you don't want thing's tripping. You're going to get that anyway off the walls, and you get a flow down the centre, and the harder that it's turning off the wall, the faster the centre flow will be. All we physically want to do is to create a hole in the atmosphere when the piston goes down and have that air rushing in there as quickly as possible.

AutoSpeed: What other developments are there on this engine - you're limited to the type of cylinder head that you can use in the SuperCar race formula?

John Sidney: Yes, but we can use different programs in the ports, which is what we are doing here. This is one of our own programs that a company in the US does for me.

AutoSpeed: When you say 'programs', you mean software in the CNC machining centre? How do these cylinder heads differ from the other programs used?

John Sidney: Yes, in the machining centre. We're smaller in the port and we have the floor of the intake runner a little higher so it's not going in low and then going over a sharp turn-down into the valve. We've got it lifted so that it rolls quicker. The ports are smaller, but it's flowing 12 per cent more than a bigger port. It appears that we don't need as big a port as they used to come with, because the shape's wrong - it's going down and turning sharp and therefore the floor of it wasn't even working. We've raised it and got more speed in the port. The turn is not as abrupt - it's just a nicer radius.

AutoSpeed: Do you ever do any smoke testing on the flowbench, to see where the flows actually are?

John Sidney: We have done. If you're smoke testing and you have the inlet valve open two hundred thou, and you have the exhaust valve sitting too high, only half of the inlet valve will work! The intake flow hits the side of the exhaust valve. The exhaust valve has to be as low as we can get it so that it doesn't interfere with early valve lift on the intake. So what we do now is put the 45 degree cut on both sides of the exhaust valve and that has cured the problem.

AutoSpeed: Is the rod length critical in terms of side-loading of the pistons?

John Sidney: It is if you start getting things right out of whack. For instance, if you were using a 3.5 inch stroke and you had 5.7 inch rods - and you wanted to turn it to 8500 rpm - you'd probably break the rod or piston because the loading would be terrible. We're using a 3 inch stroke, and these are 5.7 inch rods. We should probably go down to about 5.5 inch rods because I'm sure that we would improve mid-range torque, because the piston would stay at top dead centre longer.

AutoSpeed: What's a typical cam for one of these engines?

John Sidney: They use around 300 thou on the intake and probably 305-306 on the exhaust, and the split between the two lobes is about 106 - 108 degrees.

AutoSpeed: Do you do any modelling with any of the engine computer simulation programs that are now available? (John looks negative and shakes his head!) You don't believe in that approach?

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John Sidney: I believe in anything, but when I get some dreamers coming in the doors that tell me that they have just worked out from their program what they need on this engine (gestures to the Ford V8) to make 680 horsepower, you just stand there and say " Fuckin' dream!". Take a Chev with 23 degree cylinder heads and with a given fuel injection system on it; someone's told me that it's making 680 horsepower on a computer program - but you could never make any more than 632, no matter what you did. And we spent fifteen years playing with that combination. So it sort of says to me that those programs are not that sharp. How do you put in that a 23 degree cylinder head flows 300 cfm of air and then you buy an 18 degree cylinder head and you put it on (the flowbench) and it flows 340 cfm - how do you evaluate that? No way is it going to do it on the engine - cos the valves are in the way of the piston!

AutoSpeed: When the injectors and fuel rail are placed right across the front of the bellmouths as they are on these engines, doesn't that drop intake airflow?

John Sidney: No - the air comes from here (gesturing to the rolled edges of the bellmouths). When you get a big oil leak on the dyno - and there's smoke blowing all around - you see the air drift up over the engine and then it gets to a point near to the edge of the bellmouth and it gets sucked around the rolled edge. A 7/16th inch radius of the bellmouth seems to be the ideal thing for a ram tube. I noticed that all of the Formula 1 engines were - by my eye - using a 7/16th radius. I got to look at the Peugeot engines in their engine crate at the Grand Prix and as good as I could guess by looking from a distance of two feet, that's what they were using.

AutoSpeed: If you look at old racing cars - Formula 1 and so on - they had injectors mounted very high. So for twenty years the injectors got closer and closer to the valves, and now they're getting further and further away again. Is there an element of fashion in all of this?

John Sidney: No! It's the different injectors that you use. You see, you can't use a Bosch 803 out above the trumpet - it just sprays in a big fan everywhere. You get reversion like you can't believe. These injectors have a spray pattern as thick as my finger way down inside the trumpet before they fan out. These Bendix injectors are expensive - there's about $2600 of eight injectors here. The TAG ones are - I believe - astronomical in their cost; they're very small and I believe that they have a spray pattern similar to these. Here's a dummy fuel rail that lets us focus the position of the injectors. Once we've done that, we've got the angle and positioning of the injectors right and then the fuel rail can be machine to suit.

AutoSpeed: So the injector aim is that critical?

John Sidney: When we first built these Fords with the outside injectors, we had the injectors fully adjustable. They were on a big frame and they could go in, or that way, that way - anyway we wanted them. So we kept tweaking until the torque peaked. Finally the ram-tubes are at - I think - twenty degrees to the cylinder head and the injectors are at 15 degrees. So the injectors just spray so that they hit the wall of the ram tube about an inch before the butterfly. The spray hits the wall and bursts out - it atomises it. We had an engine on the dyno with the injectors spraying near the butterfly; I'd go in there and move them - we wouldn't even shut the motor off - and then we'd immediately ramp test it. And then we'd move it back the other way again... That just went on for three days. We know that spraying it anywhere near to the butterfly is bad. And spraying it anywhere near to the throttle shaft is terrible - it hits the shaft and bounces back! Also - you always squirt them on the opening side of the butterfly.

AutoSpeed: With these 5 litre V8 SuperCar engines, what's the difference in power between a good one and a very good one?

John Sidney: Fifteen foot-pounds or torque and probably twenty horsepower - there wouldn't be that much between them all, I'd imagine.

AutoSpeed: Is it a case of just doing hour after hour of dyno testing, incrementally finding two or three foot-pounds each time?

John Sidney: No, no. That's just rip it up and throw it in the bin bullshit. It's wasted time. Finding two or three foot-pounds is just a waste of time. I've just been explaining to a race driver, if you're going to make a change - and for example these trumpets are 9 inches - if you're gonna make a change, change them by two inches. Bang! Make a change! If you're going to change the cam timing, don't change it two degrees. Change it six or eight - you'll either fall into a hole, or you'll find something. All the little changes are bullshit. You can say to yourself, "It's five horsepower better" - but that's not going to do anything for you. You have to make serious changes!

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