Thank you James. Yes noted. I’m going to try Evan’s Battle at the Brickyard settings first. If the EGTs can’t be kept below 700C then I’ll try the lighter inlet spring and see what happens.
As to the gearing, I don’t think that’s the issue. The engine will definitely go further in G6, but having lean seized once, I didn’t want to go above 700C and backed off. One of your fellow 175 SSE road circuit drivers on the east coast (AKRA) has hit 115 mph (185 km/h) at over 13,000 rpm on a 20/20 set up. Gets to about 112 mph on a 19/20 set up.
Can you find out what pop off pressure or spring they ran at the AKRA event?
In the absence of any other data, I’d lean towards the lighter spring. You can’t stick an engine by going too rich, it’s the safest bet and most logical one given the demands of the track.
Another thing. Perhaps further down the line, but you might find the engine responds well to less ignition advance, less compression or a combination of both in road racing.
Hey!
Absolutely, go ahead and test a lighter spring, does Tillotson make lighter springs, lighter than 42gr? I will check.
All I do is Sprint racing, so a 48gr is perfect, but for Road racing a much lighter Spring might be better, having the High at 2.3 plus seems extremely rich, so replace the Spring and see how it goes.
I’ve just checked Phillip Island track, what a beautiful place, right by the Ocean, with a lake in the middle, really nice, and 4.445 meters long, no wonder you are reaching those speeds, I only see a couple of tight bends, the rest of it seems pretty smooth, so a lighter spring might be the solution. I would try the little go kart track, it’s only 750 meters I think, but should be a lot of fun!! I need to visit that track, something else for my bucket list.
Whatever you do, do not go above 700C, you might get lucky once or twice but you are risking it… I’m normally at 680-690C and it’s perfect.
That water temperature is way too low, get a smaller radiator asap, try to keep it between 55C-60C degrees, take time to warm up the engine on the trolley, it’s winter over there at the moment, I see an average temperature of 11C-13C, that’s cold, you may want to cover the Cylinder, that should keep it warm, or at least warmer.
Let us know how it goes, and lucky you having that super awesome track!!
James, in response to your question, the road circuit driver on the east coast with the AKRA is using the base 42 gram inlet spring (and a pop-off at about 10 PSI). Having said that, he still has to manage his needle settings very carefully - not what you would call a user friendly basis. That is, he’ll start the high needle at 2 turns when first leaving pit lane (so he doesn’t stall) and then richen, as the engine warms up and water temperatures stabilise, until the engine bogs. At the same time he’s constantly watching his EGTs. Not really great for novices in a stock gearbox class. I’m going to try the lighter inlet spring/s and see what happens.
Thank you for the comments Peter - much appreciated. Yes, the Phillip Island road circuit is a special place - well worth a visit and drive (it’s fast). I can’t talk about the sprint/kart circuit - I haven’t used it and I believe it’s mainly used for rentals. On the radiator, yes, noted. I’m also going to try a pre water heater - P1 100 Series for karts).
Actually, the latest standard OEM engine package for the 175 SS here in Australia (and I now presume Europe) includes a 3 way thermostat system with a loop (apparently set at 48C, albeit it seems to start moving water through the radiator at closer to 43/44C). The main issue on temperature control seems to be the sheer size of the standard radiator - it’s a massive HB-Line by KE Technology (which does seem very well made); I think the HL-004 at 395/290/40 mm. Yes, a smaller winter version is required (taping it does not get me there, nor throwing a blanket over it while on the stand).
I tested and use the same brand of radiators, I agree with you they work crazy well! I run their race line double pass in the same size (only thinner), other than taping/curtain, make sure you are also reclining it so it’s not exposed to full airflow. From the pics it seems to stand upright, past the seat edge…lower the back support, make it flatter so it gets less air. The other part is…WAT is on the cold side, but on both screenshots you are showing lap 1 and only 12K so I assume you were on your warm up lap right? Where does the temp go from there when you really start going?
Yes, some of my racing colleagues have suggested the same thing on the reclining aspect - noted. I’m about to replace the sprint seat with a superkart version and that will, in any event, neccesitate a more reclined radiator otherwise it will foul my re-positioned shoulder/arm. As to the water temp snapshot, you’ll have to ignore the lap number. For some reason the road circuits were not loaded up into the new Mychron (whereas as in the older Mychron 5 on my Stock Honda, it was not a problem).
The upshot was that the new Mychron was picking up the kart track next door, which has the same shape as the main road circuit (which had me confused), and that’s just made a meal of the indicated laps and lap times (but fixed now). It was really lap 2 on a 4.5 km (2.8 mile) circuit - nonetheless it was warmed up to circa 45C before I went out, so it should have had some temperature by then. Even 10 laps on our local sprint track (at 1 km) I’m barely getting above 48C, so I think it just comes down to the efficiency of the radiator, its size and recline position. I’ll deal with that.
As to RPMs on the road circuit, I can get it to high 13,000s in the lower gears once I had lean-off the high needle but then EGT temps were getting high on the longer stretches. So I’m stuck. The 12,000 rpm was just a snapshot and what I hit at a peak speed (140 km/h) when I seized on the first road circuit test. The second attempt (with a new piston) was a similar (read frustrating) but less extreme experience running super rich in the first instance (but un-drivable) to me leaning out the high speed needle, getting better (this time I got to 157 km/h in G6 on a 19/21 setup at 11,600 rpm), but then seeing the EGT get close to 700C (got as high as 690C), so backing off and heading back to the pits.
Not very brave but I didn’t want a second seize, particularly with quite a few “spectators” only too keen to deliver some free and helpful “I told you so” commentary (motorsport club politics - it never ends). So, some work to do on the inlet spring weight/pop-off pressure (lighter/lower) and the radiator (reclined further and/or a smaller version).
Sorry to be reviving the topic, but got to ask, would the 46g or 48g inlet spring work in high-altitude places? Two thousand four hundred meters altitude up here, and not sure if going from the 42g to the 46g or 48g would have the same effect?
Skusa Mexico happening this weekend, and I haven’t driven my 175 since the last round 2 months ago. So, probably, will give this a try…
Totally fine, we encourage it if it adds to the topic.
Lighter\softer spring will allow more fuel into the metering chamber. So in theory you could go to a higher\stiffer spring at higher altitudes (Lower air densities)
But in the absence of any data from someone who’s tried it, I’d run the “softer” options at first since it’s a safest option.
Keep us posted, always interested to hear stories from drivers around the world.
Here is the feedback from the weekend as promised.
I couldn`t really test it. The engine felt like it was lacking gas on every corner exit, and when giving it more gas (just a little tiny bit), it was bogging on every corner exit. So we changed the piston, no result, coil, no result, changing carburation (more air, less air, more gas and less gas) - no result. Even so, we changed the inlet spring from the 42g to the 46g, and it felt a little bit better, I managed to get .3 faster, but the problem was taking me half a second a lap still.
Sunday right after midday, we got a new carb, and we replaced my “old” one right after that. The problem with the corner exit was gone - But didn`t manage to test the 46g inlet spring in the new carburettor.
So the feedback in general is, that it does feel better, but I tested it with a problematic carburettor.
Will only be using the 175 again in a month when we have the final rounds of the Skusa Mexico and will come back with more updates.
You are not the only one who ended up replacing or rebuilding the whole carburetor, as I had to do.
It seems as if some carburetors are coming out of the factory with that same problem, don’t know why?
As this season is coming to an end my tillotson was leaking more and more fuel out - I had to keep cleaning the carb + starter after each run
The carb was dry(ish) when it was new but over time developed a leak. The fuel comes out behind the throttle shaft locking plate. The same happened to my old carb. Right side gets wet, fuel drips on starter and so forth
As theres only one O ring on the throttle shaft - situated next to throttle plate - the aux fuel channel isnt sealed from both sides. Over time the steel throttle shaft eats away the aluminum bore - The clearance gets bigger and bigger - more fuel residue gets outside
So during the past weekend machined the throttle shaft to accept another O ring - right beneath the locking plate. The aux port is now between two O rings.
Tested this mod today. I was able to turn the high 15 min leaner than the last time I was driving. On top of that the weather was colder so I should have had to richen the mixture
The carb / starter didnt get wet anymore during the day - all looks nice and dry
This is interesting info. I’m curious what feedback IAME/Tillotson have on this. Maybe I’m out of the loop, but it’s the first I’ve heard of the issue to that extent, and also the first time I’ve heard someone implement that solution. Good stuff!
