Popular Post Roman Posted May 11, 2022 Author Popular Post Share Posted May 11, 2022 I got the 2nd half printed and bodged it all together with a sea of cable ties and shitty wiring. But there are still bonnet clearance issues that I didnt notice earlier, caused by one particular crossmember bit on the bonnet frame. It ends up hitting on the center section that joins the two halves of the outer rails. So not really possible to use these trumpets unless I tip the motor over a bit or something. I'm thinking it might actually work to mount the outer fuel rail onto the radiator crossmember instead. But this means any future plans of fitting an airbox wont work. I could mount the injectors in through the side of the bellmouths instead, from the bottom. This would certainly make it less of a visual abomination, and also mean I can take up more of the space with runner length if needed. But I'd like to see how it goes with a straight shot down the runners, even if just temporarily. Also I wired up the other 4 injector drivers again, but after the previous fix I've still got the same issue. If I put the injector plug on number 4, it holds the injector open. Doing some googling, this is typical behaviour of a failed mosfet. So I'll see if Dad is able to take another look, otherwise I'll send it down to Link for repair. So a bit of a bummer for a few reasons, but will get something sorted. One thing I noticed though, from just giving the car a bit of an idle area tune on the outer injectors only. Even with just idle fuel, the outside of the throttles gets super cold. Like 3-5 degrees kinda thing. Then when you turn the motor off, they slowly come back up to temp again. Interesting! I wonder what it will be like after a full throttle run, maybe this is where the benefit comes from. (if anything) I'm also incredibly surprised at how well it can idle running on just outer injectors as well. 10 1 Quote Link to comment Share on other sites More sharing options...
Beaver Posted May 11, 2022 Share Posted May 11, 2022 Get a second bonnet and pull the bracing off where it hits? Because racecar etc 9 Quote Link to comment Share on other sites More sharing options...
Yowzer Posted May 11, 2022 Share Posted May 11, 2022 Time for a carbon fibre hood / 3D print one in 20 pieces 6 Quote Link to comment Share on other sites More sharing options...
Spencer Posted May 11, 2022 Share Posted May 11, 2022 Glad you are messing with outboards again. From what I read pretty much all the gains are from the charge cooling from the fuel phase change. They dont put them on bikes and race cars for zero reason. I mean we have old mates beams as a IRL example, he picks up like 10hp on his beast motor with 80-90% outboards, I just made that up beacuse CBF looking but its close to that. Most race car shit will run heaps of fuel pressre and spendy injectors to make it all work real nice. 2 Quote Link to comment Share on other sites More sharing options...
Muncie Posted May 12, 2022 Share Posted May 12, 2022 Stand the whole arrangement up like an IDA Webber on a rotang and chop a hole on the bonnet. 4 2 1 Quote Link to comment Share on other sites More sharing options...
Roman Posted May 12, 2022 Author Share Posted May 12, 2022 Yeah I guess I can do some dyno testing with bonnet up and then make some decisions from there. Will also print another revised version with injectors lower again. But hopefully get a decent spread of fuel under/over the throttle plate. The BMW airbox turned up today as well. It's super cool with the dual stage trumpets... But also definitely does not fit. 3 1 Quote Link to comment Share on other sites More sharing options...
HighLUX Posted May 12, 2022 Share Posted May 12, 2022 Sounds like time for a Puerto Rico drag spec carbon bonnet with a massive bulge to fit the doorts 3 Quote Link to comment Share on other sites More sharing options...
HighLUX Posted May 12, 2022 Share Posted May 12, 2022 Much like how this car gives me a massive bulge 1 2 Quote Link to comment Share on other sites More sharing options...
Roman Posted May 12, 2022 Author Share Posted May 12, 2022 Speaking of such things. Guess what I saw last week. A Quest4 built EP82 drag starlet with a 3SGTE. Car was never finished but the whole front shell came off, but then the whole motor and trans was mounted in such a way you could swap out the whole front. So they could race it in NA and turbo class just by swapping the front. Should have grabbed a picture, it was quite cool. 5 Quote Link to comment Share on other sites More sharing options...
GARDRB Posted May 13, 2022 Share Posted May 13, 2022 12 hours ago, Roman said: Speaking of such things. Guess what I saw last week. A Quest4 built EP82 drag starlet with a 3SGTE. Car was never finished but the whole front shell came off, but then the whole motor and trans was mounted in such a way you could swap out the whole front. So they could race it in NA and turbo class just by swapping the front. Should have grabbed a picture, it was quite cool. Kyrie is a very clever dude. He was talking years ago about building a st202 celica drag car with a Subaru gearbox with a 3sgte hanging off the front of it like the American Pro FWD cars with all their weight out in front of the front axle line. Pretty sure he's mostly doing production fabrication these days coz companies are much more reliable to deal with than car guys. 1 Quote Link to comment Share on other sites More sharing options...
Stu Posted May 13, 2022 Share Posted May 13, 2022 A mate of mine owned that from last time I saw, pretty cool 1 Quote Link to comment Share on other sites More sharing options...
cletus Posted May 13, 2022 Share Posted May 13, 2022 This one? 3 Quote Link to comment Share on other sites More sharing options...
Roman Posted May 13, 2022 Author Share Posted May 13, 2022 Yeah! Pity it was never finished. Guess it was around the time where the arse fell out of the (4&rotor style) nz drag racing scene. 1 1 Quote Link to comment Share on other sites More sharing options...
Popular Post Roman Posted May 15, 2022 Author Popular Post Share Posted May 15, 2022 After about 8 revisions I've made something that fits, doesnt hit the bonnet, seems sufficiently strong on the fuel rail support and blah blah. I've basically run out of other filaments at the moment, so all I had left was a roll of ABS+ that I've not been wanting to use because it stinks when you print it. But it's actually printed quite nice without any warping. But I think it goes a bit soft from exposure to fuel after a few days. So first thing I did is get the motor tuned to be 100% bang on fuel target, using the injectors and fuel rail moved to the "inner" position mounted on vacuum side of the throttles. So when I move the rail and injectors to the outer position, I can look at the comparative lean/rich condition. If it goes lean everywhere, it's probably a bad sign - means I'm losing lots of fuel to reversion or something. I dunno, see what happens? Well, surprisingly, after moving the rail. Is pretty well bang on. Interestingly there are some areas where it's now running rich, rather than lean. Better fuel mixing? The car drives, cruises, and generally behaves just fine. It hasnt felt super soggy on the throttle or anything either, but I have beefed up the accel enrichment a lot. This is a full throttle run, with injectors placed on outer position. You can see the lower rpm area where it runs a bit lean - this is probably where you'd want to use mostly inner injectors instead. Then start phasing the outers in after that. When driving it, the car's felt like it's more eager to get to the redline. Virtual dyno looked to agree, to the tune of about a 5hp bump towards redline. But I think I need to do some more testing before I believe the initial results. Once I've got some less dodgy trumpets printed from a better material, and my ECU fixed. I'll see if I can get back to the dyno and do some proper comparisons. 31 2 Quote Link to comment Share on other sites More sharing options...
BiTurbo228 Posted May 27, 2022 Share Posted May 27, 2022 Hey man, @yoeddynzpointed me in the direction of your thread over on Retro Rides. What a read! I was wondering if you might want to be a guinea pig for some of the stuff I'm working on around tuned length runners. It's got calcs and stuff, and I'm sure there's a graph or two that could be knocked up from it For a long time, I bought into the idea that inlet pressure waves were caused by air piling up against the back of the inlet valve as it closes and bouncing backwards and forwards along the inlet at the speed of sound until it reaches an open valve again. Apparently, according to the bods on Don Terrill's Speed Talk who are much smarter than I am, that's not how it works at all! (or, rather, that does happen but it's nowhere near being the dominant effect). What actually happens is the piston creates a strong negative pressure wave as it reaches its point of fastest acceleration (usually somewhere around 84-90 degrees of crankshaft rotation). This propagates up the inlet until it reflects off the atmospheric pressure at the end of the inlet and returns as a positive pressure wave back towards the inlet. What you want to do is size the inlet tract so that positive pressure wave arrives back at the tail end of the same stroke that created it, when the piston has slowed right down at BDC, or has even started coming back up the bore. So far, so easy to calculate. The issue is that the atmospheric pressure the wave bounces off at the open end migrates down the runner a distance that's dependent on the strength of the negative pressure generated by the downward movement of the piston and the diameter of the runner. As this is the complicated stuff that programmes like Pipemax does and I haven't worked out yet, the best I can offer is to get into the rough ballpark for trial and error, with the possible suggestion that if it's not possible to fabricate a short enough runner, you can step up the runner diameter to make it appear shorter to the pressure wave. I've made a little calculator so people can plug in their engine's specs and get a rough idea of what inlet lengths to aim for, and which ones to avoid. You'll need to know your target rpm, your stroke, your rod length, and your cam timings (actual measured cam timings, not advertised as they're often quoted in deliberately obfuscated or incorrect ways). Ideally your inlet temp would be useful too, but that's not too tricky to estimate. It's a little crude at the moment as I've no idea how far the atmospheric pressure travels down the inlet, but it should give you a rough range to aim your inlet tract length to. Would be dead interesting to compare the numbers the calculator spits out to the various different lengths of trumpet you've used. I think the only thing that would need to be measured is the length of the inlet tracts and the opening and closing times of your cams/valves (would need to be measured using a dial gauge and degree wheel, published specs are usually junk). If I can work out how exhaust length tuning works then it'd be interesting to see how that matches up as well. The usual aim with exhaust runner lengths is to tune them for the trough caused by your tuned inlets so you get minimal reversion and a smoother torque curve. If one or other of your inlet or exhaust runner lengths are dictated by packaging then you could try and tune the length of the other one to compliment the length of the one you're restricted on... Sorry for the wall of text! 3 1 Quote Link to comment Share on other sites More sharing options...
Popular Post Roman Posted May 27, 2022 Author Popular Post Share Posted May 27, 2022 8 hours ago, BiTurbo228 said: stuff Hello! Thanks for the post. Over time ive seen more and more and more of my calcuations and expectations etc unravelling when compared to real life testing. One really interesting thing regarding tuned lengths, which is covered in the video below a bit. I designed some trumpets which had a theoretically ideal bellmouth on them, but, these are too big to fit side by side. So I added a little bit of a curve to stagger them like this. So these didnt actually work out amazingly great, in fact, they were pretty much equalled or beaten by a set of poorly fitting peach cans jammed on the intake. (?!) The interesting part though, was that since I had such a large graduating elliptical shape to the bellmouth. The tuned point at which the wave reflects seemed to be somewhere deeper inside the shape. Not right at the outer end. So they behaved like a much shorter runner than their geometry would suggest. So if I'm using some calculator to tell me how long to make my runners, is this calculator complex enough to take into account how elliptical the entrance is? If not, then its going to spit out the wrong information right from the start. So then you need to do some testing anyway. So why not just do testing anyway? Another issue is that this motor has the crank offset by 14mm towards the intake side, in the block. So the accelleration rate of the piston going down, is different to the piston going up. So the maths for working out peak accel becomes more complex than if it were centered. So without taking this into account, calcs would be wrong again. Also on my previous intake setup, the intake runners had a 90 degree bend in them. If I am working out the tuned length, is this the shortest inside length? Centerline length? Or outside length? How does the speed of sound travel around a bend like this? More brain bending and more complexity to add to a model. Since we're not talking about something deeply theoretical like aligning a space telescope, and empirical testing of different lengths is incredibly easy. Especially in the era of 3d printing. These days I will always prefer to just do some work and test some iterations rather than rely on calculations which cant possibly capture the real life complexities involved. Does the speed of sound travel faster along the inside edge of a curved runner? Honestly I have no idea. But I can make curved runners and see how well they work (or not) It's like, using VVTI to adjust the cam angle. I dont care about, nor can I accurately calculate, all of the theoretical interactions that result in XYZ cam angle giving the best power. But I can move a cam to a particular position, and see that it makes good power. So thats where the cam timing goes. Sounds like a bit of a pea brained approach, but it's actually acknowledging and making peace with how insanely complex all of the contributing variables are. It's nice to delve into some theory but it's just too damn complex to accurately calculate. I think you will find it fascinating to watch basically every single video on the Garage 4AGE youtube channel, hosted by our very own @kpr. It's all amazing stuff, and seeing some real life iterative testing has absolutely crapped all over a lot of my previous expectations. A lot of things that I previously thought would matter a lot, just simply dont. In this video below, he iteratively tests a whole big bloody stack of inlet lengths and shows all of the dyno plots. This might be an interesting data set for your calculator. It's also interesting how much power his 1600cc makes with some incredibly long runners, much longer than most people ever use. 15 2 Quote Link to comment Share on other sites More sharing options...
Yowzer Posted May 27, 2022 Share Posted May 27, 2022 Theoretical improvements yield real world disappointments 4 1 2 Quote Link to comment Share on other sites More sharing options...
Yowzer Posted May 27, 2022 Share Posted May 27, 2022 Reminds me of a story from my old boss, building up a 2L Fiat twin cam race motor. He did all the math on cams intake and exhaust runners to get maximum power. His mate built the same engine with slap together parts and guess work. Guess which was the better performer of the two? 4 Quote Link to comment Share on other sites More sharing options...
tortron Posted May 27, 2022 Share Posted May 27, 2022 Would have been fine if the fiat was a perfect sphere in a vacuum 3 1 Quote Link to comment Share on other sites More sharing options...
kpr Posted May 27, 2022 Share Posted May 27, 2022 Not much to add since @Roman has it covered, Although a graph would be nice? The few bendy runners ive used. the centerline measurement seems to line up pretty well with a straight runner. in regards to length tuning 5 Quote Link to comment Share on other sites More sharing options...
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