supertib

trial and error

FYI almost all engine show the same pipe preference.... Picco and Nova will make their best peak on the same setup

1QwkSport2.5r

Thanks Neal. Any chance you have some headers on-hand that you've said dyno well and measure their length for me? My resources are limited, so I am not really in the position to buy a bunch of headers to find the one that works the best. On the flip side - if the header is too short, what could be done to the engine to better suit the engine to the pipe/header? I understand if the pressure wave returns to the exhaust port too soon, this can cause problems with how the engine behaves. I also understand there could be "trade secrets" involved with this scenario, so if you can't share the information necessary, I get it.

1QwkSport2.5r

Here are my two jewels side by side. Both are very nice engines. I like the fit and finish of the Picco better. The main turnoffs are the exhaust ports being funky and non-standard as well as the engine mount needs to be shimmed to fit the Picco in an LST. The other problems for either engine from the performance (horsepower) standpoint is the choices available for headers in the LST trucks. I have medium length and long length conical on-road headers from Novarossi as they are the only nova headers that have the bends necessary to work in an LST. The downside is they are quite short and as such may require some port work to get the header/pipe to jive with the engine. My plan is to use a medium conical Nova header and Dynamite 086HS pipe on the Picco and a long conical Nova header and Nova 9886 pipe on the Nova .28. Should make for an interesting summer!

The header picture is the medium length on top of the long one to show the difference in length. These are roughly 1/2 to 1/3 shorter than the stock LST header.

I had to turn the carb around on the Nova so the linkage would work in the truck, but they idle speed screw is now in front above the clutch & flywheel. I don't believe it will be an issue other than possibly modifying the spur/clutch cover.

For the guys that think cheap engines are still cheaper than the big name ones, think again. That Nova (Rex) Legend 28-8 is $169 at Novarossi Direct. Last I saw, a Big Red .28 was the same price on eBay.

supertib

I think your on the right track with the medium and long conical onroad manifold.... both engines will love the 9886.......... I recommend resetting the head stack on those engines and bring them down to 0.4 mm , then using a medium and colder plugs... like a P6TC, P7TH on the Picco and a C7TGC in the Nova ......

check out how nice the Nova's backplate is with the inner o-ring on the OWB shaft.... crazy good value for a engine like that

supertib

its hard to accurately measure the manifolds... for sure without any question the offroad are longer, so I do think your on the right track with using the medium and long onroad manifolds......... as I said already adjust the head clearances and run them at 0.4 mm or 0.016" between piston and button...... I use a dial indicator to set this .....

1QwkSport2.5r

The Picco came from the factory with a .4mm head clearance, the Nova is .35mm stock. I haven't found a source for Picco plugs, so I was gonna start with some McCoy MC8 and MC9 plugs in the Picco and I ordered several C6TGC plugs with the engine since that's what Nova recommended for that engine.

The one-way starter shaft has a pretty stiff fit out of the box, but I bet it will seal good. I think a properly fitted one-way shaft and bushing will seal adequately with the right fuel mix and a good needle setting. After all, the oil film is what seals the front bearing of the engine and not the flimsy rubber shield installed in the bearing.

supertib

how are you measuring clearance ? as the Nova is far from being 0.35 mm stock...it is closer to or slightly above 0.6 mm.... the Picco will be between 0.5 mm -0.6 mm ( some were even higher )

1QwkSport2.5r

The Nova head button protrudes into the cylinder 3.75mm without shims and the piston is 3.5mm below the top of the liner at TDC. It came with two .3mm shims. Id have to look back at my notes on the Picco. It seems some Picco .28 engines came with varying numbers and thicknesses of shims, but mine has two .2mm and one .1mm shim under the head.

I use a digital Vernier caliper to measure. I don't have any depth micrometers or dial indicators unfortunately.

Anthoop

Easy way to check head clearance ( I am sure you know) is to use a length of soft solder....and angle it through the plug hole...compress then measure ( you can alter orientation to try to account for piston rock)...there are other methods also but none of these static measurements will ever be of much use.

supertib

Myself I don't trust the solder method as its really difficult to get the solder to the exact perfect outside of the sleeve , and if the solder isn't touching the outside your not getting a accurate measurement...

the best way to do it is with a dial indicator down the glowplug hole... indicate and zero off the piston at TDC then indicate the button on a flat surface.... easy as can be and extremely accurate....

supertib

So the other day I did some dyno testing and decided to do a manifold vs pipe test all on the same engine.. I took 4 offroad manifolds and 4 offroad pipes...... So first I tested 4 different pipes all on the same manifold, then I tested 4 different manifolds all on the same pipe....Ends up the manifold makes a much bigger difference then the tuned pipe, I pretty much already knew this but I was definitely surprised by how dramatically ... so the engine I used was a Modified Novarossi Rex Paloma Ltd and the pipes were all Novarossi 9886,9853, 9901, 2096 and the manifolds were 41001, 41032, 41033, 41021

1QwkSport2.5r

Someday I'll get a dial indicator. For now, I roll with what I got. My caliper may not be 100% dead accurate, but it's what I got.

1QwkSport2.5r

The manifold changes the tuned length more dramatically than the pipe does. The overall length of the system is what determines your power. The pipe and its shape/number of chambers will have an effect to some degree, but the length is the ultimate determining factor.

supertib

So just to double check I just measured a couple 28-8's ..they sit at 0.62 and 0.64 mm ..... using your caliper you were in the 0.3 mm range which is way off the mark

1QwkSport2.5r

So how is the math not adding up then? Button depth is 3.75mm without any shims, piston is 3.50mm below the top of the liner at TDC. There are two .3mm shims. All I'm measuring is the space between the top of the piston and the very bottom edge of the heat button at TDC.

supertib

TDC is 3.6mm

Button is 5.79mm - 2.29mm = 3.5 mm

add 0.6 mm shim

giving a measure clearance of 0.70 mm that shifts to 0.64 mm once head is clamped down

1QwkSport2.5r

I'll remeasure my button.

1QwkSport2.5r

I must have mis-wrote my measurements in my notes. After remeasuring the button, I too got 3.5mm button depth without shims. My apologies for the confusion.

My tool showed 5.80mm - 2.30mm which gives 3.5mm.

Nitrovein

It looks strange how the 41032 drops off rather abruptly... To low EGT?
Thinking a colder glow plug might help, but it might just be the way it is I guess.

Also Very strange how little difference there is on the power band with the different pipes, not what I've seen before.
Is it a less sensitive engine?

1QwkSport2.5r

I'd love to see some dyno results using the onroad conical manifolds on these big .28s since they seem to be a fair bit shorter than the off-road manifolds are. I'm shooting blind with my LST engine/pipe swaps because I'll have no way of knowing I'm getting the best power from them. I'm gonna bet the manifolds are too short.

supertib

A colder plug may indeed help... sadly I am all out and need to order more of those....and yes...it also my be a lower EGT then ideal....power does shift around as the pipes heat saturate ..I could put a sensor onto my exhaust a monitor that fairly easily...

its a rowdy Novarossi 7 port , usually fairly sensitive

Nitrovein

I was just contemplating why the curve looked like it did, no need to do a re-run.
They play a lot with pipe heat on larger two strokes, we are less fortunate with our glow ignition.

I'm not saying you or your dyno has made an error, I just find it very odd that there is so little change in the power between the pipes.
Kind of makes you wonder why there is so many to choose from, if you can run say a 2084 or a 9886 and have pretty much the same result.

1QwkSport2.5r

I would lead me to believe the overall pipe length is pretty similar between a lot of pipes bein tested/used. We know that some factors influence the speed and intensity of the pressure waves within the pipe, but the overall length of the exhaust system can have a dramatic effect on power. It would make sense that a shorter system will perform better on an engine with higher timing than it would with milder timing.

Nitrovein

In a way you're both right and wrong at the same time...
It's kind of like saying that a sprinter is fastest with the right shoes, of course if they are to short or to long he will not run as fast. But one should start by describing his feet, as those are the design parameter, the shoes is the solution.

There is a reason why 8/10 successful 4 stroke tuners has started with 2 strokes, understanding wave tuning is one key to success.
Start out by reading some books, then try to understand them, learning them can be done by anyone.
You will soon see why there are so many misconceptions.

There are also forums that deal with these subjects in more detail, as well as webpages (it doesn't have to be all books that you read).
And it's all a friendly suggestion, I'm not trying to be a smart ass.

1QwkSport2.5r

I was speaking more from a general perspective, as with anything there are variables that will affect the scenario. But I get it nonetheless. (From a general perspective.. )