INVADER - Nitro Slash drag car

[johnnydmd]

Couple of pics before I race it next weekend and dirty it up. Actually doing some testing this weekend too and try to get a good throttle curve set up on the radio for how the car is built now.

Next Sunday, the 25th is our second list race of the season. Expecting a bigger turnout that List #1. My bro-in-law officially takes the reins of Incinerator (Nova) for good.

 

[Greywolf74]

Couple of pics before I race it next weekend and dirty it up. Actually doing some testing this weekend too and try to get a good throttle curve set up on the radio for how the car is built now.

View attachment 167362

View attachment 167363

Next Sunday, the 25th is our second list race of the season. Expecting a bigger turnout that List #1. My bro-in-law officially takes the reins of Incinerator (Nova) for good.

This has got to be one of my top 5 all time favorite builds!

 

[johnnydmd]

Bunch of updates to this car. First, and foremost - tire/wheel change. Had to. You can see why in this pic.

Thought there was enough clearance, but when the suspension compressed fully, it would catch the pipe and run up it. This really became evident on the very hot list race day where the tires not only were softer, they expand in the heat some. I was launching great, then kept veering left at 60 feet or so. Through for a loop at first, until I saw the tire get scuffed. So I reverted back to using Hoosiers with bands (I prefer this setup to belted Reactions, there is less ballooning). I picked up a set of SSD super lightweight aluminum rims to match the front SSD's perfectly.

This was a perfect fit. The tire cannot rub the pipe, and I still have about 3mm clearance from the body.

Oh, notice...the engine.

Yup, that's a Hobao Hyper 30 turbo. I needed a spare engine, and I was also looking to upgrade the carb for my SH .28-8 (there really isn't a good upgrade I could find other than modding an OS carb, so no). I and another racer using the SH .28-8 noticed several times that the tune is not easy to hold on that engine - due to the thin alloy carb not providing much heat resistance. Some thread mentioned the Hyper 30 as being great at holding tunes, so I just checked out the specs for fun. 16.9mm stroke, 19.35 bore - 38k rpm. Well, damn, that's a high revving short stroker, big displacement engine, so I snatched one up. Gonna see how this does and probably make it my primary engine with the SH as the backup. So far in break-in, I concur that it at least holds a tune well. Sounds like a chainsaw. Only question is will the short stroker lack enough low punch in comparison to to the SH .28-8? Hoping the .02 extra CI displacement helps with that. Top end power should be vastly better. It's got a carb restrictor, might play with taking that off as well and blasting more air/fuel. Might not be necessary though.

I also have been working on Invader I and putting it back together. It's close.

 

[johnnydmd]

Both Invaders are completed, and tested...mostly.

The Vette is mostly what I call a spare-parts junkyard build, but I think it came out pretty clean, other than the links which I'll replace at some point with the same kind I have on the Viper.

The Vette was testing great, until I had no brakes. Pad disintegrated somehow. Seemed to be made of a much more fibrous material than other ones I had. It launches a bit softer than the Viper despite having a slipper eliminator, probably because using the 32p gears with 3 shoe clutch. It still scooted down pretty good though. When I got home I whipped up a brake pad on the computer and cut it on my router out of CF.

The Viper was launching extremely hard. I only did 60ft passes, really didn't want to chance wrecking before the race Sunday.

 

[Doom!]

Now you need to figure out how to race yourself with a TX in each hand! Lookin' hella good.

 

[johnnydmd]

Now you need to figure out how to race yourself with a TX in each hand! Lookin' hella good.

Actually my brother-in-law will be taking the wheel After his undefeated run last month, I'm a little nervous, lol.

 

[turbo27]

Bunch of updates to this car. First, and foremost - tire/wheel change. Had to. You can see why in this pic.
View attachment 168370

Thought there was enough clearance, but when the suspension compressed fully, it would catch the pipe and run up it. This really became evident on the very hot list race day where the tires not only were softer, they expand in the heat some. I was launching great, then kept veering left at 60 feet or so. Through for a loop at first, until I saw the tire get scuffed. So I reverted back to using Hoosiers with bands (I prefer this setup to belted Reactions, there is less ballooning). I picked up a set of SSD super lightweight aluminum rims to match the front SSD's perfectly.
View attachment 168371

This was a perfect fit. The tire cannot rub the pipe, and I still have about 3mm clearance from the body.
View attachment 168372

Oh, notice...the engine.
View attachment 168373

Yup, that's a Hobao Hyper 30 turbo. I needed a spare engine, and I was also looking to upgrade the carb for my SH .28-8 (there really isn't a good upgrade I could find other than modding an OS carb, so no). I and another racer using the SH .28-8 noticed several times that the tune is not easy to hold on that engine - due to the thin alloy carb not providing much heat resistance. Some thread mentioned the Hyper 30 as being great at holding tunes, so I just checked out the specs for fun. 16.9mm stroke, 19.35 bore - 38k rpm. Well, damn, that's a high revving short stroker, big displacement engine, so I snatched one up. Gonna see how this does and probably make it my primary engine with the SH as the backup. So far in break-in, I concur that it at least holds a tune well. Sounds like a chainsaw. Only question is will the short stroker lack enough low punch in comparison to to the SH .28-8? Hoping the .02 extra CI displacement helps with that. Top end power should be vastly better. It's got a carb restrictor, might play with taking that off as well and blasting more air/fuel. Might not be necessary though.

I also have been working on Invader I and putting it back together. It's close.
View attachment 168375
View attachment 168376

I just love that car. Hard to believe what you can do, when you try.

 

[johnnydmd]

Both Invaders had issues in the last two list races. I was having issues with the Hyper 30 in Invader 2, and Invader had some bugs from being a fresh build (somewhat).
Looked good doing it though:

Had all kinds of issues with mostly the engine, not running right and struggling to get a tune. Once I got that, started having issues with the suspension and steering. All sorted now though. Just took investing a little money and getting a little better parts overall. Now I'm trying to get the shift point dialed in and had an issue there that needs sorting, as the shift grub screw fell out - thankfully not ruining the transmission in the process, guess it is in there somewhere though.

I was having issues with the Hyper 30 on the big end. It was leaned out really good, and launched hard but when the RPMs got high, it really turned pig-rich and bogged down. First instinct was that the return line was too short, and probably needed a much, much longer one. So instead of coiling up a bunch of tubing, I simply added an expansion tank.

That paid off immediately as I could tell the engine was easier to tune and it stayed more consistent. I liked it so much I did it to Invader 1 as well, and it helped that .25 nicely. Looking at old videos I did notice that both the .25 and .28 were belching a good bit of blue smoke at higher rpms. Those engines are moving a lot of air for a 2.5 oz Jato tank made for a small block. The .30 is moving of course even more air, so that fuel pressure is off the charts. But, it still wasn't 100% right, so while out testing a dude comes up to watch who knew nitro and full sized engines, and noted that he thought the air filter was the issue, that it was a little too restrictive. So I rolled the dice and took the thing off and gave it one test pass and the car screamed on the top end. Ran home, and grabbed a less restrictive one and re-tested and it was really good.

That filter was decent, but I think there are some better filters out there, so I found one that I think is and got it ordered. I did do about a dozen really great passes running this one though.

Running the black body for List Race #5. Going to do a new blower with LED's like I did for Hissed Off too.

 

[turbo27]

Nice lookin car for sure.

 

[johnnydmd]

Put together a new fake blower with lights like I did for Hissed Off so that I can run this after the sun goes down early/late in the season.

Got the new filter on. Removed the trans brake. Servo died (again), and I really just wasn't using it. It's too tricky to time it without it loading up the engine, and I rarely used it anymore.

Took it out for some testing and man did it run great with THAT filter! Got one more list race this season, and with the car currently sitting at #3, I think it's got a great shot to get back to the top.

During my testing though, the transmission locked up. Ugg. Took it home and disassembled it and found that the set screw in the input shaft gears had backed out and was jamming into the case! I was lucky it happened just putting around, had that taken place on a full pass it would have probably done some major damage. There was a little minor groove in the case and some aluminum shards/dust I had to clean out, but that was it. Looks like my dumb ass forgot to loctite it.

And this is why we test...

 

[Doom!]

I think you are reverse engineering alien technology at this point.

 

[johnnydmd]

Made a few more changes at the 11th hour. Custom made a header from an offroad pipe to try and get some more clearance so that I could fit the Mambos on the Baad Racing rims safely. I just couldn't get those early in the season launches out of my mind. They were beastly.

My only concern was that the shorter pipe might hurt the bottom end of the engine, but after firing it up and a couple of tweaks on the needles, I found that wasn't the case at all, and the throttle response actually improved quite a bit. Top end is definitely better, really woke this thing up actually. Happy accident. Obviously now a ton of clearance to hold those big meats.

Went back to the green two-toned body but swapped out the wing and blower from the black body. No reason other than I just cannot make up my mind. Wife made it up for me, lol. Swapped the wing because there is no question there was far more downforce with this one than the one, I made myself.

 

[johnnydmd]

Whipped up another spare body. Really like how this one came out, though the logos for some reason are a little less vibrant. Silly inconsistency from the sticker company I was (key word, was) using. Just need to put on the struts for the front splitter and then it'll go into a box for safe keeping.

Even though my primary race body has been in several wrecks, it's still also pretty mint yet after I buffed out the scratches. These things hold up pretty well for the most part. The black body has been in the worst of the wrecks, and does have some unfixable minor damage, but still also in good shape.

I spent this Tuesday in our local stadium parking lot testing the hell out of this, and Invader 1. Long enough to get sunburnt. The Viper launched extremely well with the big tires back on. I'd describe it as "violent" in the way it snaps the front tires up, bangs the wheelie bar, snaps them back up, bangs the bar again, pretty much porpoising the first 30 or 40 feet, then lifts them back up again at around 70 feet when it hits second gear. Top end feels good, no more bogging, and the engine is definitely loosening up and feeling like I'm getting more out of it. Since I've got another week or so before racing, I've got one other thing to test, which is the new Reds GT clutch I ordered. These are adjustable without removing anything, and I'd like to try seeing how hard of a launch I can get with the big tires. Because the road was relatively hot (80 deg air temp and sunny), I had the slipper pretty tight (1/4 turn instead of 1/2 like I usually do) and it was still launching straight. Those big tires seriously hook up well. Lotta people don't like them because they aren't belted, but with tire bands these don't balloon much.

Invader 1 had issues again. It was screaming out of the hole, almost like it was geared down short, and getting very squirrely, revving high, and acting just weird. It sure sounded fast but wasn't - not even fast enough to hit second gear. Clutch bell was squealing too and felt jammed against the shoes. Took the bell off, and the shoes had slipped upwards and against the bell. Looks like the nut I was using had a very slight taper, and was causing them to ride up, and thus rubbing against the bell and not coming fully out as the rotation of the bell was pushing them back in some. I switched the nut and will try again, but I also might use the clutch from Invader 2 when the new one for that car shows up (Reds Tetra).

 

[johnnydmd]

Reds GT clutch experiment was "fail". It's really not a great clutch for drag racing. I wound up finding a correct nut for Invader 1, and I had that car screaming. In fact, screaming too much, it was wild, and nearly uncontrollable. I quickly nuked the spur gear.

Slipper eliminator, plastic spur, that's what you get when you throw 4+ hp at it. It was also very clear that using the slipper eliminator was what made in nearly undriveable. I swapped it out with a beefy Mod 1 40/18 setup and re-tested it. Much, much better.

Did a bunch more testing on Invader 2. Made a number of chassis and engine tweaks. Had some great hits. Then a dreaded barrel roll resulted in the destruction of some rather expensive wheels.

Bent a front spindle too, luckily the expensive front wheels were ok somehow. Surprisingly no other damage. Went to my LHS, got a new spindle, and they had some JC Mambos in stock, and I had my previous bead lock rims handy, so I put it all back together and got back to it. I stuck to just doing 60-80 foot tests so that I ensure the car is intact for our final list race on Sunday. The Hobao Hyper 30 is really starting to come alive now.

 

[johnnydmd]

Whole bunch of updates on this car.

First, re-tooled the black body for an alternate style and functionality:

Less downforce, and presumably more top-end on a windy day. This was verified by a simple "wind tunnel" test.

Nitrous system installed:

I have deleted the trans brake, and more difficultly, the parachute. I simply just wasn't using them enough to justify the weight. I'm taking a little bit of an approach for 2024 that is hard for me, and that is trading bling and gadgets for performance. In 2022 this car wasn't challenged very much in our list races. 2023 was different. Everyone on the team got a LOT faster, and the gap was closed, if not passed by, literally. Hell, it wasn't even the fasted car I had any longer. So with that in mind...

I'm changing out the front alloy bulkhead for a black plastic one. Changing out the (very) heavy STRC alloy rear arms for plastic. I will (probably) leave the front arms alone, as I do need some weight to remain in the front. Rear bulkhead I'll leave as alloy to help with traction. I'm also ditching the rotostart and replacing the rear plate with a sealed one - bumpstart only from now on for this car. Also ordering ceramic bearings and will work on the sleeve some (just smoothing and polishing). All in all trying to get this lead sled down to 5.5 lbs.

The engine I'm hoping will be north of 40k rpms. It's 38k stock, being a short stroker. The COPS starter is a good bit of weight on the crank (over 10gs). Between that and the ceramics, and the porting, should be achievable. It's already a pretty decent top-end car as it is, but this, along with the nitrous shot, will make it a wild one. The challenge now will be concentrating on radio tune and tire conditioning/prep to get it to stay hooked up. The downforce using the Viper ACR body definitely helps here. The car has officially run in the low 2's with dry tire. My goal for some time has been to get it under 2 seconds, and I think that's probably just a formality, I want to see something that is closer to the records for dry tire. Whatever it takes.

 

[ahr43]

Nice rigs, johnnydmd. "Two cool shorts standin' side by side. . . " A line taken from a '60s era hot rod tune, if I recall correctly.

Rest of the guys caught you up, did they? Time to get serious now. As if you weren't before. Doubling down on performance for 2024. Anxious to see either of these cars break 2.00sec.

Said you dispensed with the chute. Probably a good thing. Back in the day, at least with electric, a chute tended to lift the rear of the car (and tires!) clear of the track surface when deployed. Do you have an A.B.S. (automatic braking) feature on your radio? Using that with my cars helps slow it without swapping ends in shut-down.

Great work carrying the nitro drag racing flag. Keep it up and good luck. Cheers. 'AC'

 

[johnnydmd]

Nice rigs, johnnydmd. "Two cool shorts standin' side by side. . . " A line taken from a '60s era hot rod tune, if I recall correctly.

Rest of the guys caught you up, did they? Time to get serious now. As if you weren't before. Doubling down on performance for 2024. Anxious to see either of these cars break 2.00sec.

Said you dispensed with the chute. Probably a good thing. Back in the day, at least with electric, a chute tended to lift the rear of the car (and tires!) clear of the track surface when deployed. Do you have an A.B.S. (automatic braking) feature on your radio? Using that with my cars helps slow it without swapping ends in shut-down.

Great work carrying the nitro drag racing flag. Keep it up and good luck. Cheers. 'AC'

Thanks!

Yeah, they sure did catch up, and I loved seeing it.

You're 100% right on the chute. It's dangerous to use, even with the hole cut out in the center. I really only used it in emergencies, like if my brakes were out of adjustment, or broken somehow, and that was not very often. It was a cool novelty to have too.

I do have the ABS feature, and I'm going to play with that. To this point I'd just been setting the braking very weak, but this feature surely would be something for me to set up.

 

[Doom!]

Sounds like your headed in the right direction. Sucks when you add all the cool gadgets and then realize they are holding you back.

 

[JCsRCcar]

Where are you from where there are two nitro cars within any distance from each other. Last time I saw a drag nitro car was 30 years ago.

 

[johnnydmd]

Where are you from where there are two nitro cars within any distance from each other. Last time I saw a drag nitro car was 30 years ago.

Maryland. We've got about 10 guys on our team right now. There are large groups of nitro drag racers in the south and have been all along. IMDRA came back a couple years ago after being dormant a few years as well. Nitro groups in Texas too for years. Puerto Rico has a large group too. We've found other groups in PA and Jersey that want to race us.

This year, there were nitro drag racing events every month in our region, nearly every weekend during some stretches. Mostly Carolina, Georgia and that area aside from what our team was doing.

Nitro SE and dry tire are the two fastest growing segments of RC drag racing. Even events that in the past have been electric only are opening up nitro classes. When I started this thread four years ago, it was very bleak, and remained that way through the worst part of Covid. Amazing how things turned starting in 2021.