Wow, this is an old thread...
I've raced 2 types of 4 stroke powered cars against 2 strokes. One was at club level races at my home track, and the other was all over the Pacific Northwest in a series that averages about 200 entries per round. I run a Perry VP-30 fuel pump and WildCat HeliMix 30% fuel in both.
Car 1 is a Kyosho Ultima ST type R (2WD gas truck) with a heavily modified FS26-C. I've never raced it in a series for 2 reasons: 1, it's not legal. 2, it falls apart every gallon or so.
The reason it falls apart is because I moved the intake port from the back of the head to the side, and the intake manifold is held in place with JB-Weld. The alcohal in glow fuel attacks epoxy-based glues, so after about a gallon, it simply falls apart.
This truck is VERY competitive running 30% full-synthetic heli fuel, an OS 2 needle slide carb and bored out FS-52 muffler. Of course, it's geared to the moon, and as such will keep pace with a P-5 powered 1/8th scale buggy on the long backstrait.
Car 2 is a Traxxas Revo, which I race in the Unlimited MT class in the Northwest Championship Tour. It is powered by a modified OS FS52. Mods are:
FS40-C cam, valve springs, and spring seats
3 needle slide valve .21 2 stroke buggy engine carburetor
Surpass 90 muffler with bored-out stinger
Competition in this class is pretty tough, with most guys opting to run a TM18. There are some who run big block 2 strokes in their Revos, and a few LST drivers running the Collari .32! So far, I've not found myself wanting more power, and at most tracks I don't need more speed. I eat up the 2 strokes exiting corners, so of course I do better on tighter/loamier tracks.
This truck is very much in the prototype stage, and it's made 3 A-mains at 2-day races this year. Results of those races were 6th, 8th, and 4th. At the 8th place race, I set fast lap in qualifying and felt like I could have won, right up to the 11:30 mark when the transmission let go. I was in 2nd at the time and the guy in 1st ended up breaking. I'll get 'em this year!
The FS26C compared to the NovaRossi .12 I used to run has faster throttle response, more controllable power, and has this wicked little kick right when you think the engine's going to sign-off in over-rev land. You can see this on MXWrench's dyno charts of the modified 4 stroke on his website. In Dyno-land, it's a nice little peak. On the track, it's a power-lift at the end of a medium size strait. The 4 stroke also gets better fuel economy.
The FS52 compared to the 2 strokes I race against has more bottom-end accelleration, instant throttle response, but runs out of gear on a bigger track. It just can't breath as well as the FS26C, so there's not as much power on top. I've got taller gears on order for next season. 15/38 is stock. I was running 19/36. I will be running 20/35 next season. It has worse fuel economy than the TM18s, and about the same as the .28 - .32 big blocks.