kpr

Im getting pretty good at melting pvc into shape. although melting some electrical conduit and down pipes into a plenum maybe beyond my capabilities. whilst fumes created being the death of my last few brain cells I do keep forgetting to wack the hilux plenum on there. would probably do ok

Yeh think may pursue the big tapered idea. The 45's look decent in some places. But not so keen how jumps around so much. Kinda cool how can see it brick wall soon as run out of airflow in the runners. Someone bring said beams here and will dyno it for a small fee

Results are in on the downsized runners.

Bit louder than normal, which is all the loud. sounds like a deeper dort. Yeh it does some silly stuff around there when get too out the gate with length or small diameter so i found out.. 80kw at 4000rpm is pretty lol though

So.. I haven't got the pipe yet to finish the downsized runners, so in the meantime

From my testing, a full bell mouth that rolls back around on itself is unneeded. diminishing returns over anything more that a basic bellmouth that barley makes it to 90deg. I thought this maybe as you say something to do with my setup. the runners being oversized for the engine meaning the bellmouth has less effect. But some preliminary testing yesterday on a runner that is too small for the engine basically acted the same way. a small flair on the end got it close to what a full bellmouth can do. Still have more things to try before come to any conclusions, and as you say my conclusion may not work on another engine. Ive seen downsizing of the runner work on a similar engine to mine, but it maybe band aiding another issue

Haven't bothered trying it for reasons @Roman suggests. If was dedicated race car would have likely tried it already. Still would be interesting to see if has as much benefit as what old mate had on the b16a I can say if you are going to do it. move them far as possible, going actual outboard. moving my injectors back from head about 50mm to the throttles had zero or at least un-measurable effect. Probably also want to go bigger than 700cc. got 980cc's on mine (dont ask why) and thats 40% duty on pump gas. I'm assuming you will be making more power, so to get in window to avoid stand off, probably need something bigger

Have done some butchery with some more power duct. This is same as one of the ones in last test (51m id). but ive cut a section out of some more pvc and slid it inside. making 46mm runner, will slide a second one inside make 41mm. just need to acquire some more to cut up

Yeah but sounds like half of them break stock.

attempting to get big torque numbers on a small engine at low rpm. pump gas wont be your friend. and the engine also wont be your friend. you'll be running big cylinder pressure which is hard on everything. not saying your idea isn't possible, but will never have big amounts of torque right off the bottom.

Going to do a round 2 on this soon, since i've forgotten how long it took last time. Same deal as last time, you can send me stuff and will test it. Pretty much anything goes this time. Main thing i will be testing is smaller diameter trumpets, which i will likely make from pvc or anything else i can find in the correct diameter. If have any dumb ideas novelty items etc.. or think you can build something that beats everything in the last test, send it my way. My normal intake will be the baseline everything is tested against. Will probably do the same thing on a stock blacktop 20v fwd format, at some stage also. which maybe of more benefit to most people, that haven't spent half their life polishing a turd. (not saying a 20v isn't a turd, it definitely is )

If had a pipe that fit tight in the tail pipe, would work good. but yeh obviously would only work on one sized exhaust. so getting it right up there is a good compromise. also only the tip of the sensor needs to be in exhaust flow. so a long boss for the sensor to screw into is good. can help with sensor overheating/cooling

diameter doesn't need to be very big. I made one from 25mm box as thats what i had hanging around. the longer it is the better. as further can jam it up exhaust more likely to get a accurate reading.

Wouldn't think so, not at wide open throttle anyway.

Haven't had anything to do with stock ecu tunes or barras, so of no help there. but kinda sound more like a tune issue, if your mate complained about it after it was tuned. changing the cooler piping generally wont mess with the tune that much. probably worth taking it to someone who knows there shit for retune, if has some kinda weird fuel model wizardry as roman says. possibly also more cost effective to go that way to diagnose a potential issue than buying the hp tuners stuff and/or throwing parts parts at it

If it drove like that straight after it was "tuned", yep sounds like the dude has done a shit job. If was fine after the tune for awhile then started playing up, might be a bad sensor or the likes rather than tune

too many diffs aye. the front one will go down!

going by your drawing. can you lift the rear of gearbox up and drop the pinion down so your angles are less aggressive ? the hanger will have to be moved up as well obviously. Or possibly leave the gearbox where is. run first shaft up at 2.5deg angle from the gearbox, so the flange on end of first shaft is at zero deg. then drop the diff nose down to zero deg also. which should get you pretty close doing some rough maths. all depends if you can do that in your tunnel though reason for running a very small angle on the first shaft, is because it has no 2nd uni to cancel out how the uni accelerates and decelerates the shaft when run on an angle. sub 3 deg is fine. running a zero best, but yeh, uni will wear fast since doesn't have and bearing rotation. to much angle will cause more problems that running none. as @Mof says the rear shaft angles need to be matched. ideally the less angle the better, long as it has enough angle to keep the uni's happy. the nose of the diff will want to rotate up under acceleration. but from memory you are running rose joints on the 4 link? if so wont get bugger all deflection. so set up neutral will be fine

they dont like moisture/ water much, so if for any reason has been subjected to it sensor could be stuffed. otherwise as above make sure you dont have any janky wiring that could short from 5v+ wire to the map signal wire. bad ground may do it also

You still want to richen it up as load increases. if stay lean with too much load will run into heat and knock issues. will basically end up same as what you would use in a car. its more what the motor wants than what its in. will depend on the whole setup as to how much load is on engine at "boat cruise" . from memory the supercharged mang machine i tuned, once got up on the plane and backed off wasn't a silly amount of load on engine. so the afr could be fairly lean at that point the link map i was thinking of must be in the g3 software. g4 has vvti version. dont have it installed on this pc at the moment

there is a pretty good base map in the link software, one we used would have been in the older g3 or g4 pclink. that only needed a few tweaks to get right, on a mates 1uz years ago. maybe worth a look just to get the trend of the fuel map. plus some ideas for the ignition map. compare to old mates one you found

cold start idle thing probably isn't too much of an issue in jet boat, since you would be generally in the boat manning the throttle soon as its started.

Map looks horrible. I would suggest disconnecting the shaft between the engine and jet unit if possible. So you can run the engine while out of water. Tune as much of map as possible free revving it and getting all the idle stuff right . Then yeah from that guess the rest of the tune. A stock engine without cams will have a fairly smooth map with highest numbers being at max torque. Once in the water, as you say will only be able to tune certain part of the map, the way the jet unit loads the motor. I would do part throttle runs. Once get that right . Repeat at higher throttle. Right up to full throttle. Then use trend from the points you tuned to guess rest of map. Need to sort the main tune before bothering with any of the compensation