LRP ZR.28 Spec 4
 

So, 10 years or so after the release of the undeniably awesome LRP ZR.28 Spec 3, LRP now has a Spec 4. Anybody have one?

I see in the description they have tried to improve the idle characteristics with a new carb, and it's listed as a 6+1.

Unfortunately the old nitro MT days are mostly gone. Still, anybody got one? I'm in a holding phase out of nitro cars for a while, but am always still interested.. Same top end as the Spec 3, really better idle, will all the old backplates fit, run time, etc?..

Nitro Motor ZR.28 Spec.4 Pullstart | Product | LRP Home


I think racing is so mega-lame. Too much time required, too much money, too many over-serious Stiffly Stiffersons involved (i.e. fun-killers), etc. Such a shame that MT bashing died off. There are hardly any good trucks on the market now to put this thing in....

And yeah, electric has some advantages in terms of sound and ease of use. But just like with real cars, they will never have the soul of a real fuel-burning high-revving honest to god mechanical engine...

Long live nitro. :D

Come to Florida, and we shall bash.

I might get one of those spec 4s. It will probably end up being a blah blah with a different head on it (like typical) but who knows!

Ha - I'd like that...

The Spec 3 is listed as an 8+1:

Nitro Motor Z.28R Pullstart Spec.3 | Produkt | LRP

This changed, because I think they used to be listed as a 8+2 or something, but the engine gurus said the second exhaust port didn't count or whatever. But iirc, the Spec 2 was a 6+1 port. As was the Dynamite Big Red .28(which I had, and which was good also.. - though I think not quite the top end of the Spec 3/454)

Whatever the case, in my experience the ZR.30X is the best MT engine I ever had, mostly because of the carb. It idled like a race engine. Smooth, low, and constant. My LRP Spec 3, 454, Big Red, and all my Mach 427's and Sportwerks 26's were great performers, but would load up and cut out if you left them idling. They were still all great engines for the money, and super easy to break in and tune, but the idle was often a bit sketchy. Not so the LRP ZR.30X. Maybe the new Spec 4 is the same... I wonder if it has the Spec 3's top end.. Which, when tuned right, is awesome in an MT. 10 (!!) years ago, people were saying the Spec 3 was as if made for the LST2.. And it did run (and sound) great at full tilt in an LST2...

I don't even know what current trucks would be worth putting a new engine like the Spec 4 in. I would imagine LST nitro parts (engine mount, tank mounts, clutches, etc..) are getting hard to find. I'd love a brand new LST2 to put one in.. I probably have enough spares to get a new chassis up and running. My two trucks are just thrashed though. Probably 15 gallons between both of them.. - and multiple engines, clutches, diffs, trannies, etc..

The Big Red is my current SH based mill, and it's far softer on the bottom than any of my other big blocks. That MAY be due to the Ofna buggy header I'm using coupled with the fact it's in an XL with taller gearing but I don't care enough to investigate honestly!
As for what truck...
My buddy got an Arrma Talion. It would be trivial to convert that thing to nitro. I googled it, and I dont see where anyone has converted ANY Arrma stuff. (Probably because electric is so fast ha)

My rigs are worn out too. Every diff cup, every suspension pivot point, ect. Loosey goosey.

Worn out? I call that bind proof.. XD

The Talion is just a truggy. I have an RC8T.

For me a basher MT needs a 2-speed..

Yeah? You should see the death wobble my XL gets at high speeds! Haha

Can't disagree there.
The only single speed truck I own is my Bullet, and it's got a fourstroke on it (more reason I should convert it to 2 speed I suppose).

Anywho, I am really considering picking up this new LRP. It's hard to justify though because all of my trucks have good engines on them at the moment and I even have a couple NIB engines already sitting around that I got for some reason or another.

Trust me, I know how it is..

I'd give it a miss then.. Wish I would have given lots of RC (car) things a miss over the years...

I just bought one from Germany and I'm expecting to arrive in a few days, hopefully in time to break it in this weekend, it's all in the hands of DHL :) I will install it in a LST XXL, with its original pipe and header. I will let you know how the whole process went through

Any updates on this? Im curious if the spec 4 is any better than the spec 3. Is it really less ports or are they just advertising it like this because the extra ports are just bypass ports? If it is less ports id imagine it doesn't rev as high as the spec 3 .

Not yet. But this weekend it will be done. I will open the engine anyway and will take some pictures, if you want

The Big Red was supposedly a modded Spec 2, but for all I know they were identical. In terms of performance it was very good. If anything, maybe a bit less top than the Spec 3, which on paper anyway makes sense, since the Spec 3 had more ports... Overall I'd take a 3 over a 2..

I'm not really an engine guru or anything. I just know what I like. It would interest me though to know if there is a difference between the Spec2/Big Red and the new Spec 4, and if so, what are those differences? Is it really an all new engine? Neither the Spec 2 nor 3 were +1's afaik...

What I can do is to compare the spec 4 with Losi 454, which is a spec 3, if I'm right.

That would be great, from what I understand the 454 is basically a spec 3. Looks like lrp is dropping a 32x spec 4 which I'm guessing is replacing the 30x. I'm kinda sad that they discontinued the 30x.

The 30X is the best MT engine I ever had for sure..

The Spec 3 was awesome for the money - and had great top end. And like all LRP's was easy as heck to break in and tune. The carb though could have been a bit better. Like on the 30X.

That said, I was amazed the last few times I ran the 454 in my LST2. It idled perfectly and ran great.. It really ripped to a degree I wasn't quite expecting. Go figger'.. And this was after long periods of not being run...

What other photo sharing website are you using, beside photobucket? You know, considering their new policy ... Flickr is OK?

Here you go:


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<a data-flickr-embed="true" href="https://www.flickr.com/photos/9855019@N08/35013375343/in/datetaken-public/" title="DSC_1072"><img src="https://farm5.staticflickr.com/4257/35013375343_431c32025e_k.jpg" width="2048" height="1152" alt="DSC_1072"></a><script async src="//embedr.flickr.com/assets/client-code.js" charset="utf-8"></script>



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If you ask me, the cylinder are identical, port wise. I didn't measure them, but there is the same ports number and size.

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The end of the crankshaft seems to be a little different. Unfortunately I couldn't take the piston out, the conrod haven't enough play/space to get out from the crankshaft. Maybe because it is a brand new motor, but how the heck did they installed it???

<a data-flickr-embed="true" href="https://www.flickr.com/photos/9855019@N08/35782819086/in/datetaken-public/" title="DSC_1076"><img src="https://farm5.staticflickr.com/4229/35782819086_b85fc4b9f6_k.jpg" width="2048" height="1152" alt="DSC_1076"></a><script async src="//embedr.flickr.com/assets/client-code.js" charset="utf-8"></script>

I installed the old rotostart and I had to install the old start shaft, the new shaft is a few millimeters thicker at its hex end.

Sweet thanks for the pics. have you had a chance to break the motor in yet?

Yes, I broke it in last weekend. Around 10 fuel tanks. It was kind on annoying, couldn't keep it on idle only to find out two of the shoe clutch springs was broken :) I thought it was because the setting was too rich, happily I didn't over leaned it. Temperatures
between 60°C and 90°C with a cloth wraped around the cooling head. I ran the first tank on the bench with help from a heatgun, just to be sure of the temperatures. Three or four stops with the piston on BDC for heat cycle. Hopefully I will run a few more tanks tomorrow, if it woun't rain too much.

Ok sweet, keep us posted on what you think. If it's like the spec 3 but with better idling I'll pick one up for sure.

My lhs actually had a lrp 28 spec 4 in stock so i threw it on layaway with them. Ill pay it off in a week or two and throw it on my savage x. im pretty excited to try it out. My f4.6 is a good running motor but man it runs hot.

There you go! https://youtu.be/uIk56dsUMDw

I still can't pull a wheelie and the only thing I can think why is this happening (or why not) is the strength of the clutch's springs, maybe they are too weak/thin and the motor doesn't have the time to rev up enough for a higher torque. I would say the carb's settings are rather on the lean side (When I checked the glow-plug it was just started to turn grey on the outside), although it seems is a little rich on the LSN, as you can hear at the first throttle. But when I pinched the fuel line, it started to die after 1 - 1.5 sec, way too soon if you ask me. HSN was 1/4-1/2 turns counterclockwise from the point where the engine would start to cutoff.
The temperatures was just OK (spit method), outside temperature around 28 Celsius, 25% HPI fuel and LRP #5 glow plug

Checked the vid, but seems to me as if its stuck on 2nd gear.

No, the gear shifting is ok. You can hear a perfect gear shift at 1:05 and again at 3:14

It's still soggy rich from idle to high throttle; and at idle it sounds like the idle gap is too wide. It sounded like it was idling too fast. It should idle low and sound a bit lopey.

I think I'll reinstall the original back plate, not the XXL's rotostart. Even though the 454's Pull/Spin Start Shaft is pretty new, there might be a little leak around it. But before this, I'll change the exhaust gasket, it was completely broken, I don't know how I didn't saw that. But not too soon, I just broke my foot, so 3 to 4 weeks... no RC :D

If the aluminum backplate has an o-ring and the o-ring is soft and not broken, it won't leak in most cases. If the bushing in the backplate is worn, it may weep some oil, but that shouldn't cause any tractability problems unless it's badly worn.

i have one of the lrp 32 spec 4 going on a traxxas revo