BHP

[Marc Fenner]

Whats good BHP at the engine in a race engine?

[Marc Fenner]

Wow is it that hush hush.

Just wanting 6to see if our engine was up to scratch or if i should be on the look out for another engine.

Ball part figure will do!

[Paul Robertson]

depends where you have been to the rolling road marc dave walkers 41/42 ,pete baldwins 45/46

[pat collier]

depends.... also Pauls figures are at the wheel, dynos at the flywheel, also varies on the atmospheric pressure of the day... etc etc etc
A better indication is the torque curve you get, the curve should be a smooth uplift with the club cam
effectivly if you are getting upwards of 44 at the wheels with a good readable power band then the engine is ok if you can get more bhp with the same torque profile then obviously you are better off, but if you get a high peak bhp but with cliff faces either side then you have something seriously amiss

there are a whole bunch of things that we looked at before we decided on the engine design we use, despite outright bhp being an obvious goal it was not the only one

Fun and games

[TerryCollier]

Hi

Following Paul and Pat's replies I would like to confirm that both are true. A specific figure is difficult to get except through an engine dyno. The problem is that a rolling road is not a rolling road due to differences in rollers and adjustment of the rolling resistance that is done. Our use of a single rolling road was to provide some measure of consistency in measuring progress (or not).

When I began looking at engines I started by considering what I wanted an engine to do. Obviously go fast, but what does this mean? One of the key problems is the fixed nature of the gear box. The other was the need to get the 2CV to accelerate, not an easy task due to the gear box ratios.

Check this one out. If you change gear from 3rd to 4th at 6250 rpm what rpm are you doing in 4th? Similarly for 6500 rpm? Take your range readings from the rolling road and check the change in power output. Is it accetable? For example, if you have 45HP at 6500 but fall to 37HP when you change then you are not competitive with the front runners. You will lose ground coming out of accelerating corners and down long straights.

I came up with a target for my engine performance. The key rev band was between 4500 rpm and 6500 rpm. I needed to be able to change up from third gear into fourth but still be able to hit a high torque zone. Most racing 2CV's did not do this. You can still hear and see the problem if you stand at a track opposite the gear change point. Most engines go temporarily flat on the change and then pick up. Some drivers I have spoken to confirm this even if they have to go out and check.

My final engines have a curve that rises only 8% over the range 4500 to 7500 rpm. Obviously my peak HP is adequate. This gave us the smooth constant power plus a lot of grunt to get up the odd hill. How I designed and assembled the standard bits to get to this point is another story but it took a lot of time and a quite expensive learning curve.

I will give you two more tips -- one is obvious but is not always thought about the other is straightforward.

Using the rolling road measures the output at the wheel so does not tell you exactly what the engine is doing. The figure is the net effect after all of the loss in power between the engine and the wheel. Energy lost in moving residual weight and friction. Significant gain can be made by consideration of lubrication to reduce friction and by removing much of the residual weight -- the flywheel is an obvious feature.

The second point you may like to consider is the crankshaft. My motivation in doing anything with a crankshaft started when I had one go on me in an early engine. The damage caused was both very costly and time consuming. Although everyone told me that this was a rare event, once was too much. So I thought that checking every crankshaft before I put it into an engine was sensible good housekeeping. This was especially true when you consider that like most people I was using old engines with many 000s of miles of driving as the base point. So I managed to find someone who would strip a crank down and check the bearings for undue or risky wear and where possible replace them and rebuild it. This paid off as I discarded over 20% of cranks as too risky. However, as a by product we found that many of the cranks were out of balance on reassembly. An out of balance crank will reduce power output at the wheel as some will be used to fight the attempt at oscillation. Correcting this tends to smooth out the curve rather than give more top HP.

If you want to try this then contact

Chris Ackerby on 01268 776642. Mention that Terry the 2CV bloke suggested you call and that you have a crank that needs looking at and he will do a job for you. It will cost in the region of £85 plus transport costs or you can drop it in which is what I do. He handles crank design and fabrication for many Bike racing Teams as well as four wheeled ones which I am sworn to secrecy about.

Sorry this is long but that is my problem. I have found that there is no short answer to getting performance out of the 2CV. Balance is a key word there is no bolt on recipe for winning.

Regards

Terry Collier

[Marc Fenner]

Thanks for all your help. It has helped alot. Not sure if to be worried or not. The guy who rolling roaded our car had another 2cv in theweek before with a New Richard Dalton engine in and my engine had a few more BHP than tha. However our other engine had less. Stupidly i didnt get a print out of the runs but the guy who done the runs seemed to think they where good engines. He has had experiance in the past with them. A guy called Tom in Hampshire. Should i be worried and looking for another engine?

[Catherine Noble]

NO!

C x
:wink:

[Derek Coghill]

Marc, will it give you a decent amount of power and last for 24 hours?

Yes?

Good. Can I have some of the spare power then please?

[Geoff Archer]

Wow is it that hush hush.

Just wanting 6to see if our engine was up to scratch or if i should be on the look out for another engine.

Ball part figure will do!

remember its not only power but youve got to have a driver to drive!!!

[Francis Rottenburg]

True.... but a bad driver and a quick engine is a lot faster than a bad driver and a slow engine!  Also quite interesting to see who was quick in the wet at Snet and who wasn't so quick.  Of course there is always the set up of the car that makes a big difference in the wet but rain tends to be an equaliser.  Unless your name is Sparrow when you have at least 2 seconds a lap on everyone.

[Pete Sparrow]

Ever tried using a mini digger Francis?

Me nether but the point to be made is that the machine is only as good as the operator so I have to disagree with you.
In one of my mags (bike actually) they gave a Honda fireblade (very quick 1000cc sportsbike) to someone that had been riding 2 years and a Honda CB 500 (commuter bike) to a BSB racer and then went for the best lap time round Mallory to prove you point. Have a guess who was quickest?
This is why i will always love Gary Adnitt

[Catherine Noble]

:D :D :D

Marvellous ... there's hope for me yet then? Ok maybe not ...

C x

[Geoff Archer]

in fact a bad driver in a fast car is a menece!!!!!!!!!

[Marc Fenner]

well i gues i will find out soon what my engine is like when i start racing it. If its cr*p then i better get saving for a Geoff Archer special or one of pauls engines