Lotus Elan

Nitrous In A Twin Cam

PostPost by: rgh0 » Mon May 30, 2005 11:31 am

Hi Keith

You asked me to have a look at whats possible with nitous oxide boosting a twin cam. So I had a quick look at the question with the following conclusions

1. A 25 to 50 hp boost on the standard engine appears achievable.

2. The rule of thumb with Nitro boosting is to keep the BMEP below 300 psi to avoid detonation. In a standard twink 1 lb per minute of nitro plus matching extra fuel generates 25 extra hp and BMEP is below 300 psi from 1500 rpm up. 2 lb per minute give 50 hp and BMEP below 300 from 3000 rpm up. A long duration cam can help by reducing low rpm BMEP without loosing top end hp if you want more power still.

3. Doing the above is going to stress everyting else in the engine such as head gaskets, cooling system, pistons, bearings so the rest of the motor needs to be in good shape and in comparable condition to a competition motor

4. A 150 to 180 hp racing twin cam develops its power at higher revs and lower BMEPs. Heat load is similar, pressure load lower, inertia loads higher. Overall my guess is its doable. Probably dont need a steel bottom as the crank and rods and bearings probably good for the increased pressure load ( maybe). Biggest problem probably head gasket sealing.

I had a great weekends racing coming sixth outright. The 7 litre Corvette and Shelby Mustang were too quick for me but I held out the 6 litre Iso Rivolta. Roger Eland in a Marcos won in the main race. But this is the same guy and car that used to beat Tony Thompson in the UK when he was winning the sports car championships in his 26R so Roger knows whats hes doing. My new engine ran perfectly with no leaks at all. Just need a dyno session as its running leaner than my previous engine on the same carb settings.

regards
Rohan
In God I trust.... All others please bring data
User avatar
rgh0
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 7163
Joined: 22 Sep 2003
Location: Melbourne, Australia

PostPost by: type26owner » Mon May 30, 2005 7:44 pm

Thanks Rohan,
I'm at like a lambda of .7 and would shoot for 1 with the added gas. Does your program allow you to input those sort of values?

Great to hear your outing was pleasant one. Just geting out there being a rolling piece of artwork is the most important goal IMHO.
type26owner
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1616
Joined: 18 Sep 2003

PostPost by: rgh0 » Tue May 31, 2005 9:38 am

The dyno simulation software I use makes fairly sweeping assumptions around fuel and combuston. The detailed modeling is primarily around the flow process of air / fuel in and exhaust gas out based on bottom end dimensions, compression ratio, cam profiles and cylinder head flow data

It assumes the air fuel ratio you are using is optimum for maximum power and fuel suitable for the compression ratio specified and that optimum ignition timing for maximum power is used throughout the rev range. It does not specifically model the combustion process.

For nitrous injection it models the hp and torque boost compared to the non nitro model based on a specified addition rate of nitro per minute and assumes additional fuel as required for optimum combustion of the fuel / air / nitro mixture.

Rohan
In God I trust.... All others please bring data
User avatar
rgh0
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 7163
Joined: 22 Sep 2003
Location: Melbourne, Australia

PostPost by: type26owner » Wed Jun 01, 2005 1:21 pm

Rohan,
Kinda figured the software would behave in that way. Looks like the cheapest way to try this is to buy a 'Sneaky Pete' kit. Only two hours is the predicted installation time, yeah right. :rolleyes:
type26owner
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1616
Joined: 18 Sep 2003

Total Online:

Users browsing this forum: No registered users and 6 guests