The AJP V8!16Valve

[speed12]

Hi! Can somebody to explain me why TVR build their AJP V8 with 16 valves?That''s means 2 valves per Cylinder.Except the Tuscan Speed6 that has 4 valves per cylinder.It has better Torque at the low revs?with the 2 valves per cylinder or something?

[veryplast]

teh cylinderhead is to small.

[trefor]

Less/cheaper to repair?

[speed12]

yes it might be the cylinderhead small but the Speed12 has 4 valves per cylynder.Also they couldn't fix a biger cylynderhead?or it doesn't fit in front of the car? Also it has better torque or power with the 2 valves per cylinder? I believe that it maybe have 2 valves per cyl. but it sure it is Large ones!It's not 4 but small...

[Sparks]

veryplast, How do formula one do it then? They are only 3 litre (4.2 for ajp) with 10 cylinders. I thought it was down to simplicity and therefore cost/ease of design/repair. There must be some good reason, or there would be a head upgrade for the cerbera driver with too much money! Sparks

[speed12]

I don't think that the liters (3 for F-1)is the reason for TVR to put 2 valves per cylinder.because for the Tuscan they have 4 valves per cyl. But is a Speed6 engine so maybe veryplast has right about the cylinderhead... Or it's the performance of the motor...maybe it's beter with 2 valves per cylinder...

[speed12]

Better Torque for the Low Revs!

[JM Cerb]

The AJP V8 was developed for (in the car world) next to nothing. 2 valves per cylinder was much simpler and easier and cheaper to build and get reliable (!). Multi valve engines (eg. 4 valves per cylinder) generally have power and torque much higher and revs need to be kept up for top performance. On the track this is very noticeable and multi-valvers need heel and toe for good times.

[Graham B]

Remember seeing a topgear interview with Peter Wheeler. He said they designed the V8 with 2 valves per cylinder in order to keep the torque low down. Graham

[speed12]

Hmm!That's why they have amazing 0-100!

[trefor]

I thought I'd heard Wheeler say that they did 2 valves to keep the engine size (width etc.) down to fit it into the Cerbera engine bay ... could be wrong though. T/.

[jc126007]

I'd imagine the AJP is 2 valve/cylinder for a number of reasons. Multivalve engines with minimal torque at low rpm would be a result of the camshaft characteristics and engine capacity/configuration. The only way for a small naturally aspirated engine to make power is to rev like buggery. A camshaft that allows and engine to rev like buggery will have bugger all low down torque due to the amount of valve lift and duration required for high rpm operation. Due to its size etc the AJP v8's do not have to rev hard to make much power, so a much tamer camshaft can be used. If the engine doesnt need to rev to 10krpm then the valves dont need to move too fast, and can be big and heavy like in a 2 valve design. I'd imagine most multivalves are that way because they need light little valves, especially in F1. Also, as mentioned, F1 has a huge development budget, and TVR do not, also, F1 needs to make as much power as possible and to hell with low down torque. The AJP v8 could benefit from being multivalve, but only if it were modified to rev harder where the advantages of lots of little valves are exploited. I know this is pretty scatterbrain but eh, shoot me. Also, re: space for 4 valves, I've a friend with a 2 liter straight six with 4valves/cyliner (toyota soarer), they're minute, but they fit, and the bore is much smaller than in any TVR. I might edit this sometime when I feel like making it easy to follow.

[AdamB]

Theres a 10 pager floating around on the web written by Mr Melling on the AJP. I will try to find it and post but the gist of that was something to do with not wanting to retard the ignition. Apparently part of the reason 16v's rev slowly (the heavy fly wheel kind of rev slowly) is something to do with emisions requiring the ignition to be retared at low revs. They wanted to avoid this with the AJP's (bark bark instead of vrooooom, vrooooom ) and it was easier to do with 2 valves than 4.