Will a TRX 3.3 engine fit in my HPI car?

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Shahanand

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I have hpi nitro car ,I planning to upgrade to trx 3.3 engine is it fit and suitable for my car ?
95273
 

D3MON

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Is your car a slide carb or a rotary? If I remember right RS4s were slide and should work just fine, if yours is a rotary though would not work, unless the carbs could be swapped.
 

olds97_lss

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It's rotary I believe. I had a HPI NitroMT which was an rs4 platform, it had a rotary carb on it. I put an OS18CV-R(X) in it after finding the weird little engine mounts. It was also a side exhaust engine and I got the threaded shaft one (vs pilot) so I could use the stock bits. The stock engine on mine was bolted directly to the chassis from the bottom of the crank case. Oddest thing I ever had. Appears yours is the same. So, you will also have to find engine mounts.

The TRX engine is rear exhaust, so you will have to find a header to fit it as well.

My NMT wit the 18 in it:



Was 15 years ago. I put a 1/8" steel plate under the engine and spur gear to stiffen the chassis up some. The stock spur would strip if you looked at it funny and with all the twisting the chassis did when offroading... I'd barely get a tank or two through it before the spur died.

Now I would have used a hunk of aluminum, but that's what I had then.

Sad to say, OS quit making that engine. It was a very nice little engine. Cheap too.
 

D3MON

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Sad to say, OS quit making that engine. It was a very nice little engine. Cheap too.
was my favorite small block engine, is what i had in my Maxx.
side note: growing kinda of fond of the axial engine though, which of course they stopped making as well...
 

sv250

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It will take you 5 min to swing the servo horn 99 deg and adjust for slide carb. No big deal
 

olds97_lss

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I can't picture in my head how to get the brakes to work and the slide to work in the orientation things are on that vehicle. Yours looks like it's made for a slide carb. The RS4 isn't.
 

sv250

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That is a rs4. It came wihh a rotory carb. It currently has thc 3.3 with slide carb. Thsts why i put the linkage pic in.

Rotory or slide your still pulling on the carb. Just 90 deg different. You may want to use a 4 way servo horn. That gives you more options
 

olds97_lss

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Odd, it's setup a lot different. I thought the rs4 platform was the same across the board. Guess not.
 

olds97_lss

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They are basicly. New ones have a wider chassis and nicer radio boxes.
The engine sit's completely different and it's belt drive vs center axle, steering servo and tank are on opposite sides as well... It has 4 wheels and an engine... so yeah, that's about the same. ;)
 

D3MON

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Odd, it's setup a lot different. I thought the rs4 platform was the same across the board. Guess not.
if i remember right the original RS4 and the RS4-3 was shaft drive, and the RS4-2 is belt drive. quite a bit different betwen 2 and the others but the original and RS4-3 look to be more or less similar.
 

sv250

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Ok servos are still servos and linkage is still linkage.

Just because you can't do it, dont advise against it. Belt drive has absolutly nothing to do with linkage.

Send it over here and ill install it.
 

D3MON

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Ok servos are still servos and linkage is still linkage.

Just because you can't do it, dont advise against it. Belt drive has absolutly nothing to do with linkage.

Send it over here and ill install it.
wanted to throw my 0.02$ in
no reason at all to get hostile.... he never advised against it, just said he couldn't picture how it would work...
with enough modifications ie relocating servo etc anything would work, hell you could probably rig up a big block into the car if you really wanted to get that deep into it.
belt drive versions also have a completely different layout for servos and doesn't apply to the vehicle in question anyway.

but I digress,
i think that the carb is a rotary carb that came on the vehicle, from what it looks like you could do is as said above, either put the 4 mount servo horn on and see if it will pull straight enough and would not interfere with the brake linkage, looks like you might be able to spin the servo itself 180 degrees locating the servo rotation point closer to the front of the car, and set/adjusts linkages that way, again making sure of linkage clearances.
 

olds97_lss

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Ok servos are still servos and linkage is still linkage.

Just because you can't do it, dont advise against it. Belt drive has absolutly nothing to do with linkage.

Send it over here and ill install it.
I don't think I advised against it, just that I couldn't see how it worked. I am by no means a linkage expert. Pretty much everything I've ever dealt with was pretty simple to visualize how it would work.

I found an image of a setup like the MT2/NitroMT and like OP's that has a slide carb:


Looking at it, now I get what you were saying. I just couldn't figure it out without seeing it.

The subtlety with that one is that it uses a self breaking servo horn like HPI uses on most of their stuff, vs springs/collars for everything.
 

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