Is it possible to get a Dunerunner to rocket off the line?

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dmkolb

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I have a Dunerunner with a stock engine. It's got a Walbro 990 carb, 8K clutch and CPI tuned exhaust. A bunch of other stuff that I don't think maters for this question. I think I have it dialed in just about perfectly. The low speed needle I have played with rich and leaning to find out where it gets the best instant acceleration when you go full throttle from a dead stop. I do understand once it starts moving the high speed needle comes into play at that point.


So I had a T-Maxx with a 3.3 nitro engine in it. When the low speed was tuned right it would pull wheelies off the line all day long. Am I wrong in thinking if the low speed on the 30cc engine is tuned just right it'll have all 4 tires breaking lose from a dead stop? Maybe it's just to heavy and it'll never really do that?


My buddy has a HPI Baja and he nails the throttle and the thing breaks the tires lose without hesitation. Mine seems to have a slight delay before it starts to move. I'm mostly happy with the acceleration I just wish it would rocket off the line when I nail the throttle without the slight hesitation.


Hope I explained what I'm looking for.
 
Where can I pick up the other clutch spring? I'm guessing that's a 9,500 RPM spring? Do they make it as a clutch kit?

A new engine will be in the future when it gets warmer again. I can do a new clutch setup now though if I can figure out where to buy it from.
 
My dunerunner has the ported head and a dominator rear exhaust. It will break traction on all 4 using street tires on pavement. It is an animal! Other than the ported head, I actually took the 8K spring out and am happier with the 7,500 spring. I found it works best because we play at an old go-kart track with cement curbs and full throttle isnt always the right answer if you arent looking to break front suspension pieces.
 
Right now engine work and or replacement isn't going to happen. I have to work with what I have. So playing with those rules what if anything can be done for better punch from a dead stop other than what I have. I have a 8K clutch set up all ready installed. The stock clutch setup was horrible and very slow acceleration wise so not willing to go back from what I have now.
 
I don't have a dune runner. I do have a 5b,with the mod clutch and ddm head with the dominator pipe. It snaps off the line like a rocket. Of course it's only 2wd vs the dunes 4wd ?
 
delta_kilo said:
Right now engine work and or replacement isn't going to happen. I have to work with what I have. So playing with those rules what if anything can be done for better punch from a dead stop other than what I have. I have a 8K clutch set up all ready installed. The stock clutch setup was horrible and very slow acceleration wise so not willing to go back from what I have now.
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yea, money is getting tight. look at ddm- large scale r-c for a cy 29 cc top end on sale. I bought one for 35 dollars- just needed a intake-base gasket. this top end will walk the dog on the stock hy 30.5. squish clearence means nothing on this top end- with a stock base gasket, you can lift the xb-25 pound by the starter!! huge torque- decent overrev too.
 
The best way to be quicker is to add more power. Unfortunately big cars take big wallets. :p
 
yea, check out ada racing in arizona, they have good deals on the cy-29. by these bolts for the jug- HPI # 15438. wide head torx screw. M5 x 20 mm. about 4 dollars. In my humble opinion, this top end will hang with anything on a light car- may not beat other engines on top end power- but its pulling power is really powerful- its the way the factory machined the jug---.
 
delta_kilo said:
Where can I pick up the other clutch spring? I'm guessing that's a 9,500 RPM spring? Do they make it as a clutch kit? A new engine will be in the future when it gets warmer again. I can do a new clutch setup now though if I can figure out where to buy it from.
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Ddm have the clutch springs. You can just replace the spring no need for the complete kit.
 
Great advice guys. I just picked up a Dune Runner, my first RedCat, and am having the same issue. Dog off the line. I'm also new to the Forum.
 
Toss the stock exhaust can. An X-CAN gives the low end boost and doesn't break the bank. Gets you running nice until you figure out what you really are looking for.

That is what I've done. Future plans: OBR engine, a tuned pipe, TWO SPEED tranny! Then I'll probably cry because of driveline problems. Sigh...

Always something.
 
Got a chance to run the DR with all the intake and exhaust mods I've made.

The thing is insane now!

First, the Dune Runner. Stock 30.5cc CY engine, stock clutch. Proline HPI 5T Trenchers. Much taller then the stock tires.

Stage 1 X-CAN exhaust can.

Stage 2 Add 8" long silicone 1/2" ID pipes on the X-CAN. Replace stock air filter with a DTI filter on a tall intake venturi.

Result of Stage 1. No more 100' bog, comes off the line well. Could be better. 2X better then stock.

Result of Stage 2. Pull the trigger, the rear end goes down and all 4 Trenchers are tossing dirt. Looks like my Revo or T-Maxx (I'm NOT a "wheelie nut". Fast is when all four are on the dirt and pulling and steering. I use the throttle, not a wheelie bar. I did mention dirt. On a paved track, OH YEAH, I'd use a wheelie bar! The Dune Runner isn't there, yet.) Insane top end, I had to keep to 3/4 throttle where I used Full Throttle in Stage 1. It was on the pipe from the start. When I pulled the spark plug during post run clean up, I discovered I was still running rich, the way this thing was running I figured I had to be getting too lean. I actually backed off the tune. There is plenty of power left to tap.

Didn't break the bank getting the stock engine running well, around $120 including the X-Can.

Stage 3. Santa has an order on the wish list for a OBR 5.5 HP Pro Stock 30.5 engine for next Christmas. I've gone crazy idiot on other builds, this one I'm doing step by step for once. So the Pro Stock, which can be upgaded. I want a 4 bolt motor to work with. But there are wheel bearings, etc, issues to work out with the Stage 2 build first.

And the Stage 2 is SOOO much better then stock!

With the Killer RC Power Start, no choke is needed. A 18V drill motor spins the engine fast enough so that there is plenty of spark to get started. Good news for a new carb install. :)

 
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Went running for the first time in a week yesterday, we've been having crap weather. Not trying to do a comparison, just a run with the GoPro and have some fun. Well, I forgot to start recording on the GoPro, so no video, but during the dead time between runs I made some chassis changes, more chamber on the rear end, and tightened up one spot tie on a pipe to pinch it. Got the idea from DDM tech info by the way, where he talks about cans.

Well, it was running rich, but, after the engine warmed up... A little bog from being rich, but this was the best the DR stock engine has ever run. Way faster, it was grabbing air on stretches of trail it never did before. I was having so much fun that I got careless, ran the buggy out where I hadn't walked it out and, blam. Big chunk of concrete behind a bush. Popped the tie rod out of the left steering carrier. Servo saver worked as advertised. Whew. Big hit. But I'm waiting for a new steering carrier. Can't tighten the screw, the carrier hole is stripped. BIG HIT.

But, I had a BIG poop EATING GRIN the whole time, even when ordering the parts afterwards.

Pinching just one pipe a bit made a huge difference. Next run I'll have the engine leaned out.

Also, the Santa engine order has been changed to a "Birthday Present", OBR Prostock 5.5 HP engine is on order. When I install that, I'll build the stock engine as a stroker.
 
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Chief409 said:
Popped the tie rod out of the left steering carrier. Servo saver worked as advertised. Whew. Big hit. But I'm waiting for a new steering carrier. Can't tighten the screw, the carrier hole is stripped. BIG HIT..
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For a quick fix, get a 2 part epoxy, mix it. fill the stripped out part with it , cover the rod threads with it. insert it as far as u can. 10 min later your good to go.This gets you out of trouble for a lot of stuff.Not sure if you have the same thing over there in the US. but i'm sure you have something the same.glue.webp

glue.webp

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Been a couple of months, mods, $$$, etc. A upgrade of the Pro Stock to a Full Mod Losi torque engine, VRC Big Bore pipe, which is tuned for low and mid range torque, 8k clutch. Belt drive.

And, YES, with enough power and the right mods, a Dune Runner can rocket off the line! Possibly better than a 5ive 4x4 EVER will! No extra baggage to haul around! The Dune Runner rear engine provides good traction from the start. I've watched 5ive's at the sand drags, and think I can take 'em now. :) On a track, too much power to consider running. Dune running, I'll find out, nearest thing to a dune is 2 hours drive from here, I'll make the drive before October.

Once I replace the worn out center diff crown gear and pinion (hopefully nothing else is worn out, don't think so) I'll try to get a video made. But, it's fast, REAL FAST!

Edit: Scouted a new location for sand running on the way home work today, and Hit the Jackpot! It's in the Mojave River between Victorville and Barstow, and just a little more then an hour drive. Coarse sand, lots of OHV action looking at the tracks, but "It'll DO". Parking, it looks like I could bring the trailer and spend a weekend.
 
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