rerb Posted January 18 Posted January 18 (edited) My motor currently runs stock bandit rods, stock busa pistons, standard cometic MLS head gasket and copper base gasket. The cylinders were shaved 1 mm. I'm trying to save some money by buying hayabusa turbo pistons instead of mtcs for better internals. (Almost half the price!) The hayabusa pistons have a wrsitpin center to timing edge distance of 25 +/- 0.2 mm. Wossner K8734DA-4 hayabusa turbo pistons are 26.8mm. With gaskets installed, squish band with my setup is 1.0mm on the nose using the solder method. Deck height is ~1.25mm but it was a pain to get consistent and the squish should be the same measurement since the bandit head doesn't have a taper on the sides I measured and the piston shouldn't have "tipped" in the bore during measurment since I measured along the wrist pin axis. The compression ratio is around 7.9:1 with this setup. (Non shaved cylinders with stock busa pistons is about 7.2 using my non shaved spare cylinders as a guide) I'm going to order a 80 thou (2mm) sheet of aluminum and if it's nice and flat, use the laser cutter at work to make a cylinder spacer. My theory is raising it 2mm will increase the squish 0.2mm (since the pistons are 1.8mm taller) and bring compression to around 8.8:1 6.72:1 with 2 base gaskets. (Edit: stock busa dish is ~10cc, wossner is 17.8) Anyone see a problem with my plan or have experience with wossner pistons? I've always used them for 2 stroke rebuilds but never performance bits. Also its been mentioned before but ill back it up, if anyone's running busa pistons I'd definitely recommend shaving the cylinders 1 mm, makes off boost way better. I gained 50 hp from the same boost after doing that. Edited January 21 by rerb Quote
Gixer1460 Posted January 19 Posted January 19 I think sub 9.0:1 CR is waaaay to low for use with E85 which is as close to methanol as anything available and that needs compression and rich AFR. Query - if stock Bus pistons have 'correct' ht for your combination why do 'Bus turbo pistons' not (which should be drop- in's) ? Why are they taller and so, even in a Bus motor, INCREASE the CR not lower it? I'm confused! If it is, what it is . . . . . i'd be tempted to spacer plate only 1mm and skim pistons 0.5mm and get squish to 0.8 - 0.75mm (unlikely to over rev a blown motor & stretch rods!) and 9.5:1 CR if E85 is in constant use. Hell that CR would even work with regular 98 super unleaded if boost was moderate! 1 Quote
rerb Posted January 19 Author Posted January 19 6 hours ago, Gixer1460 said: I think sub 9.0:1 CR is waaaay to low for use with E85 which is as close to methanol as anything available and that needs compression and rich AFR. Query - if stock Bus pistons have 'correct' ht for your combination why do 'Bus turbo pistons' not (which should be drop- in's) ? Why are they taller and so, even in a Bus motor, INCREASE the CR not lower it? I'm confused! If it is, what it is . . . . . i'd be tempted to spacer plate only 1mm and skim pistons 0.5mm and get squish to 0.8 - 0.75mm (unlikely to over rev a blown motor & stretch rods!) and 9.5:1 CR if E85 is in constant use. Hell that CR would even work with regular 98 super unleaded if boost was moderate! Wossner says "base plate required" for those pistons, I got the 26.8mm number from emailing them. The bike will run pump gas 95% of the time, but for the standing mile and a half events that I plan to go to, I want it to run way cooler than it does currently on pump, and make more power, which I want to achieve with e85. I think 9.5:1ish is a good target for CR, I've had 26 psi down this motor at 9.4:1 on standard 93 (98 for you guys) with the clutch being the weak point but I'll have watermeth and a conservative tune. Only thing stopping me from being full time e85 is that I'll have to get it shipped here by the barrel... Quote
Arttu Posted January 19 Posted January 19 I have to admit that I couldn't follow all your numbers completely But I guess you are aware that Wossner turbo pistons will result lower compression than stock Busa pistons even when you set the squish / deck height the same? Also I'm wondering how you got 1.0mm squish with 1.25mm deck height (if I understood your description correctly)? Squish should be deck height + gasket thickness. Otherwise ~9.5:1 compression and 1.0mm squish sound pretty good to me. On pump gas you should be able to run it up to 15 psi, at least. Probably more with water-meth injection. And on E85 it should be good for 30 psi or so. 1 Quote
clivegto Posted January 19 Posted January 19 Don't know about aftermarket pistons but I have hayabusa mk1 pistons and rods in the Harris with B12 mk1 motor it does have a big valve flowed head though. Now if I remember correctly with a 2mm spacer plate (no base gaskets) I ended up at 8.83:1 with 0.8mm head gasket. 1 Quote
Duckndive Posted January 20 Posted January 20 Curious as to why you decked / shaved the block -1 mm As this one of a few I've done was stock everything with just gen1 busa pistons at TDC Quote
rerb Posted January 20 Author Posted January 20 On 1/19/2025 at 2:07 PM, Arttu said: I have to admit that I couldn't follow all your numbers completely But I guess you are aware that Wossner turbo pistons will result lower compression than stock Busa pistons even when you set the squish / deck height the same? Also I'm wondering how you got 1.0mm squish with 1.25mm deck height (if I understood your description correctly)? Squish should be deck height + gasket thickness. Otherwise ~9.5:1 compression and 1.0mm squish sound pretty good to me. On pump gas you should be able to run it up to 15 psi, at least. Probably more with water-meth injection. And on E85 it should be good for 30 psi or so. Yeah, I'm not sure why the discrepancy. I did the solder test a good 4 to 5 times on 2 cylinders and kept getting pretty much exactly 1mm, but my calipers would always read higher on the deck height using the depth gauge. I know the wossner kit is "tall deck" but I don't know the dish volume of them, I'll send them another email and ask to verify my numbers. 4 hours ago, Duckndive said: Curious as to why you decked / shaved the block -1 mm As this one of a few I've done was stock everything with just gen1 busa pistons at TDC Strange, using bandit rods when I first put mine together I had around 2mm of deck clearance and it was way more sluggish off boost than it is now Quote
Arttu Posted January 20 Posted January 20 39 minutes ago, rerb said: Yeah, I'm not sure why the discrepancy. I did the solder test a good 4 to 5 times on 2 cylinders and kept getting pretty much exactly 1mm, but my calipers would always read higher on the deck height using the depth gauge. I know the wossner kit is "tall deck" but I don't know the dish volume of them, I'll send them another email and ask to verify my numbers. Was that deck height measurement with or without head gasket? If the gasket was included then the discrepancy is only 0.25mm which isn't that dramatic. I'm pretty sure the Wossner turbo pistons have bigger dish volume than the stock ones. That's the main idea of low compression pistons, to get lower compression while maintaining good squish gap. Quote
rerb Posted January 20 Author Posted January 20 Just now, Arttu said: Was that deck height measurement with or without head gasket? If the gasket was included then the discrepancy is only 0.25mm which isn't that dramatic. I'm pretty sure the Wossner turbo pistons have bigger dish volume than the stock ones. That's the main idea of low compression pistons, to get lower compression while maintaining good squish gap. That was without the head gasket, I'm pretty sure that it was user error as the edge of the caliper was very small and difficult to hold straight against the deck when measuring. I sent wosser another email about the volume, I'm fine with anywhere from ~9-9.5:1 for this build, what I'm mostly trying to get dialed is the squish. I understand that with lower compression I might not get all the benefits from e85, but like I said earlier I'd only be running it for it's cooling properties. I know for a fact that longer stretches of WOT at 21 psi IATs were around the 160 mark and climbing with 50/50 watermeth spray, close to 200 pre spray according to my dual sensor temp gauge (Farenheit). However on the teardown after 3 seasons there's no evidence of detonation at all so so far so good. Main goal is to break 200+ relatively easily in the 1.5 mile event and not cook the motor Quote
rerb Posted January 21 Author Posted January 21 (edited) Made a mistake, in a hurry I used 21.5ml as the head volume instead of 29, since the forum post I was viewing was discussing the DOT head (21.5). the ACTUAL numbers are with 1mm shaved: 7.9:1 stock cylinders: 7.15:1 I updated the main post. I also heard back from wossner, the pistons are 17.8cc vs. the stock busa 10cc. Unfortunately, this setup is too low (sub 7 CR). I'm looking at their other piston options to try and find one that will fit nicely. If I can't, I'll bite the bullet on a set of MTCs. Edited January 21 by rerb 1 Quote
Duckndive Posted January 21 Posted January 21 24 minutes ago, rerb said: Made a mistake, in a hurry I used 21.5ml as the head volume instead of 29, since the forum post I was viewing was discussing the DOT head (21.5). the ACTUAL numbers are with 1mm shaved: 7.9:1 stock cylinders: 7.15:1 I updated the main post. I also heard back from wossner, the pistons are 17.8cc vs. the stock busa 10cc. Unfortunately, this setup is too low (sub 7 CR). I'm looking at their other piston options to try and find one that will fit nicely. If I can't, I'll bite the bullet on a set of MTCs. Stock 8.48:1 Quote
rerb Posted January 21 Author Posted January 21 12 minutes ago, Duckndive said: Stock 8.48:1 This is what I was using. The deck clearance is the 1mm i measured with the solder for the head to piston TDC with all gaskets and full torque, with an added mm because It was shaved. Are you using a copper head gasket? The only MLS I've been able to find are 0.030" compressed Quote
Duckndive Posted January 21 Posted January 21 (edited) Gasket was the one i removed "MLS" after it spat it out in a tantrum If your gasket is 0.030" thats 0.762mm Edited January 21 by Duckndive Quote
gmansyz Posted February 14 Posted February 14 11:1 CR minimum for any alcohol anything. If you absolutely have to use Busa pistons, get the Busa rods as well. They are about 2mm longer than the Bandits. And flat top pistons at the minimum. The Busa chamber is may 17 to 18 cc's. 12 B is nearly 30 cc's. And hope the valve reliefs are workable. Otherwise they will need to be recut. It would be so much easier to just get 10:1 or even the 12+:1 Bandit/GSXR pistons and cut the dome down to match. G Quote
rerb Posted February 23 Author Posted February 23 (edited) I ended up using a set of +4.9cc wossner std. bore tall deck busa pistons, and a set of gsxr1100 maxpeeding rods. I'm going to be running a 0.50" spacer for 8.8:1 CR and 1.15mm squish. I went lower on the CR for pump gas' sake and so i can have some more safety with tuning, a friend with a low compression turbo miata convinced me that e85 will still be beneficial for lower CRs, specifically in the cooling/high boost department. I'm definitely sacrificing some horsepower going less that 9.5:1 but i made 260 on pump at 8:1 with a very, very safe tune and about 23 psi. Since I'm sea level and I don't think the bandit has tons of valve overlap on it's stock cams it shouldn't be a huge hit to my dynamic CR. Anyways now I'm on to crank work, I was sending mine to APE but held off because I'm unsure what's really necessary. I know I'm getting it polished, balanced, and straightened, but I'm curious what peoples thoughts are on lightening/nitriding. Those two extras will add some $$ but it sounds like in return I'm getting more horsepower to the wheels and a stronger crank.. but everything has it's caveats. Any one here have any thoughts? Edited February 23 by rerb Quote
Gixer1460 Posted February 23 Posted February 23 You can't nitride, non nitridable steel - generally it used to be EN40B. Tuftriding on the other hand is very similar and can be applied to most steels. Funnily enough neither process is commonly applied to Jap bike engine cranks - they are probably superior quality when compared to other worldly products. Assuming a turbo application, lightening just makes a crank weaker but more revvy - not what a turbo wants or needs! Balancing always worthwhile! 2 Quote
rerb Posted February 23 Author Posted February 23 8 minutes ago, Gixer1460 said: You can't nitride, non nitridable steel - generally it used to be EN40B. Tuftriding on the other hand is very similar and can be applied to most steels. Funnily enough neither process is commonly applied to Jap bike engine cranks - they are probably superior quality when compared to other worldly products. Assuming a turbo application, lightening just makes a crank weaker but more revvy - not what a turbo wants or needs! Balancing always worthwhile! Gotcha, I was going off of APEs website for services and what some of the gsxr1000 guys were doing. Would've been neat to have a knife edged crank for the few extra ponies from less drag, but I'm already a little worried for how much a stock crank can take so it's probably best to avoid modding it like that. Quote
Gixer1460 Posted February 23 Posted February 23 1100 cranks can do wild hp - its usually the rods that let go and its mostly oil related. One thing that may help in that regard is cross drilling the oil discharge points in the big ends. The purpose is minimise the centrifical force on the oil at the point of discharge - done a lot in auto engines so usefulness in a bike engine ??? Bear in mind the nutcase (in the nicest possible way ) doing the 1/2 thousand HP engine (now over 1k hp) only beefed up the crank, rods and cases after he reached the 0.5k hp goal! 3 Quote
rerb Posted February 25 Author Posted February 25 On 2/23/2025 at 7:46 AM, Gixer1460 said: 1100 cranks can do wild hp - its usually the rods that let go and its mostly oil related. One thing that may help in that regard is cross drilling the oil discharge points in the big ends. The purpose is minimise the centrifical force on the oil at the point of discharge - done a lot in auto engines so usefulness in a bike engine ??? Bear in mind the nutcase (in the nicest possible way ) doing the 1/2 thousand HP engine (now over 1k hp) only beefed up the crank, rods and cases after he reached the 0.5k hp goal! Impressive, focusing on oiling will definitely be important. I took your earlier advice and cleaned out all the oiling passages, they were fairly clean but I definitely got some junk out. Once I get my crank back and measured after the polishing/mag, I think I'd like to run ever so slightly more oiling clearance than std on the big ends and run 15w 50. Are oem shells considered the best, or is there a trustworthy alternative for these engines? My oil pressure was very good before, 100+ psi on cold starts and around 40 at warm idle, 80 at cruise. Although my sensor was at the banjos for the oil cooler so I'm not sure if that's the same circuit as the engine oil or if the oil to the cooler follows a different path. Do these oil pumps wear out? Mines at 70k miles and I have a 45k mile one I can put in if pumps are known to weaken over time. Aside from that, the Earls 19 row oil cooler does an amazing job at keeping the temps down so I'm not too worried about cooling capacity, just maintaining good pressure on long stints of WOT. Thanks for the advice Quote
peter1127 Posted February 25 Posted February 25 (edited) Some turbo bikes have problems with scavenging the oil out, expecially gravity drain systems. This results in smoking. Running lower oil level makes that less critical, but with hard acceleration and wheelies this can result in oil pickup seeing nothing but air. Hard braking too. Oil level at max was fine on my previous bike, current bike I'm thinking to add some dividers to keep oil around the pickup, and/or lowering the pickup. Possibly people have done this or have better ideas? Edited February 25 by peter1127 1 Quote
Gixer1460 Posted February 25 Posted February 25 59 minutes ago, rerb said: Once I get my crank back and measured after the polishing/mag, I think I'd like to run ever so slightly more oiling clearance than std on the big ends and run 15w 50. Are oem shells considered the best, or is there a trustworthy alternative for these engines? My oil pressure was very good before, 100+ psi on cold starts and around 40 at warm idle, 80 at cruise. Although my sensor was at the banjos for the oil cooler so I'm not sure if that's the same circuit as the engine oil or if the oil to the cooler follows a different path. Do these oil pumps wear out? Mines at 70k miles and I have a 45k mile one I can put in if pumps are known to weaken over time. Aside from that, the Earls 19 row oil cooler does an amazing job at keeping the temps down so I'm not too worried about cooling capacity, just maintaining good pressure on long stints of WOT. #1 - I'd only run bigger clearances on a race engine that gets exemplary maintenance. #2 - You are only likely to find OEM shell bearings - these aren't like Ford or Chevy's that have loads of aftermarket choices! #3 - Sensor on the oil cooler line will be the low pressure / high volume circuit - 30 - 40 psi is about as high as it gets. Engine bearing oil pressure is usually taken from main gallery and can be 60psi + when hot. #4 - Anything can wear out due to wear / debris / poor maintenance etc. These pumps are usually good - i've never heard of one being replaced for anything other than damage. If the 45k mile pump is good, then newer trumps older! #5 - I used a 19 row / std width Mocal cooler on my Kawazuki which coped ok but would get bloody hot on a hot UK day, after multiple 1/4 miles or caught in stop / start traffic. Don't know what actual temps were - just too hot to touch measurement! 1 Quote
rerb Posted February 26 Author Posted February 26 Noted, I'll definitely make a proper scavenge system too other than just a gravity drain. I'll probably keep my current pump since the lower mile motor has 2 melted pistons and (at least on my cooler side) oil pressure seems pretty good still. I know my motor was well taken care of, but can't say the same about the spare. Depending on the measurements on the crank journals after polishing I'll stick with the stamped letters on the crank/block. Might end up being slightly looser than brand new, which probably works a little bit in my favor for LSR runs and thicker oil. I'm not sure of the exact dimensions on my earls cooler, but even after particularly spirited riding on an empty i95 I can keep my thin gloved hand against the block for a pretty long time. I even had issues where it wouldn't get up to temp in 40-degree (f) weather in the spring/fall. Quote
peter1127 Posted February 26 Posted February 26 (edited) I got a oil temp gauge to screw in where the oil filler cap normally is pretty useful and cheap. Easier then to check the injury/temperature conversion chart. Edited February 26 by peter1127 Quote
Gixer1460 Posted February 26 Posted February 26 3 hours ago, peter1127 said: That'll be no good - OP is an 'merican - they still use feet and pounds for temp measurements! Quote
rerb Posted April 19 Author Posted April 19 Little update, I've been really busy lately so I haven't had the time to work on the bike much. The crank is back, balanced and polished, successfully passed the mag test. $350 with shipping from APE, roughly a month turn around time from when it left my door to when it showed up. Not bad at all. I have the main shell sizing figured out, and will be measuring my rods and crank to get the big ends sorted. I got my head taken apart and wow, the seals were completely cooked, no wonder it was burning oil on deceleration, I thought it was just the Eblag turbos sucking in oil. The seats have a good amount of pitting. Im going APE springs/titanium retainers/ guides, seals, and stainless valves, hopefully the seats can be cut to the new valves, otherwise I'll have to buy bronze seats from APE. I know when using APE nuts you need to replace the washers for the heat nuts. Is this for all the washers, or only the steel ones and not the copper ones? I've bought a sheet of 4130 chromoly steel and will laser cut washers from it, should work well since it has very high creep and fatigue resistance. Just not sure if I needed 8 or 12. Quote
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