Team Lotus..I can appreciate youre idea...however what I am looking for is more scale realism that actually works on an RC car....but thanks for youre input...

I understand your point; but the fan could be mounted within/flush with the rear apron section of either a sedan or GTP style body so that it would be virually invisible. You could even but some mesh screen material over it to further conceal it. In actuality it would only be noticeable when the car is viewed directly from the rear, and even then barely!
I too am a scale realism fan; I only offered this concept as a means of taking rc car performance to the maximum. It may not be your solution, but perhaps others out there reading this might be inclined to try it.

team lotus,they used massive fans for that,the size of the chassis!ud have to have a jet to make a difference !
also ud have to a hole in the chassis to have the air sucked in

Hi,

Anyone tried mounting a touring car wing under the chassis
as diffuser ? especially nearer to the rear tires ?

Yes... mounted to the TC3 rear bumper... with the bumper cut so only two pieces jut out for the attachment of the wing... the wing being 1/8" smaller than the total inner width of the rear tires. The only bad thing was, you had to cut out the rear bumper area of the body to get full effect of the lower wing... at higher speeds the wing spilled so much air into the back of the body, it actually slowed the car. Cutting out the back of the body (not allowed at some tracks) allowed the air to flow through, and meet the air spilling off of the rear wing mounted to the deck of the body. The car was really stable at high speeds... and adding side winglets to the upper and lower wings locked the car in on high speed sweepers. The best i ever had it work was mounting the lower wing to the bumper with aluminum buggy wing mounts... and using thick wing wire to mount to the upper wing... they were going through the wing mount areas on the body. This allowed all rear downforce from the wings to be transferred to the chassis, not the body. (looked similar to a wing setup on a full scale funny dragcar, but not as elaborate) This is something similar to what oval racers do with adding the rear wing to the rear motor pod, and not the body. As mentioned before... with the onset of indoor carpet racing... most high speed traction tricks on asphalt were no longer necessary, so i havent messed with it in quite a while.
- Dave

i ran pancars back in the mid and late 80's
when it was what at its prime we built lexan undercarrieges with tunnels and rear diffusers with an opening at the front of the car to creat a vacumm effect on the car and it worked ! id say we experimented with these things here in fl for about 2 years and then roar banned them because not everybody had acess to it , as far as touring car we did try it a couple year s ago and the same thing happen roar said no. and went as far as making the yokomo guys grind away the fins and the end of the main tub on the mr4tc chassis during the sacramento paved onroad nationals.
i went as far as running a bud rear bumper and glued about six fins to it and installed side nerf bumpers made fins for that to and ran it here at the local races i say it worked cut of about 2tenths of a secon per lap but since roar said i t was illegal i never tried it again.