zredbaron

Yes. There are several parts that alter the duration and volume the accelerator pump delivers. I have personally found that the springs vary from model to model. I believe these are also an available tuning part' date=' though I have not found a part number to order a different set of springs.[/quote'] ...really? i was being sarcastic. sorry. i personally would prefer to keep the focus of the thread on fixing big picture issues [flat spot!] vice polishing areas that probably aren't even noticeable. but hey, that's me. i'm a crazy man, and i don't own the thread...

really? now the pump circuit is adjustable beyond the jet? different springs!? now we're *really* getting in the weeds... although i don't have salt roads here in VA and am still 'able' to drive, the concrete is cold enough that i can't put the power down unless i trailer the car to an open road somewhere and do it at higher speed (i prefer carb tuning in 2nd/3rd; 2nd breaks loose at about 5000 and 3rd would be unsafe locally) (2nd holds in the summer). so yeah, i might have to wait till next summer, too. the navy has plans for me to deploy to the middle east soon, anyway. i've been reading that honda thread, and they stress the importance of float levels, too. i find this promising. i still suspect an F9 (similar to F11 but leaner) would be good even after making sure the floats are right. some highlights from the other site's weber thread:

well if this is true, then that's news for me. i'm merely going off the weber book, and the weber book does NOT mention that.

unfortunately what i stated earlier about one float measurement fits all is incorrect. under the dcoe chapter, there is a table with columns for multiple parts of the float measurments. it offers production car settings for alfa romeos, lotus, lamborghinis, aston martins, maseratis, bmws, but no datsun L6s. back to the drawing board. pick one? try another and note the difference? i'm tired of this shot-in-the-dark game.

scott, again, thank you for your reply. i obviously am not content with my lack of success, and welcome [ie could benifit from] experience in the subject. i am self taught, and have never met a so-called carb guru. no doubt they do exist, but my experience is that those that i *have* been referred to [those that have been described as masters or gurus], were in fact nothing of the sort. they were merely the only person around that could get a decent tune. in my experience, i knew more about what my car needed than they did. after years of experimentation and reading, i too can get a decent tune. the difference is, i know where i fall short. where am i going with all this? even i don't know! haha. no, seriously... i agree with you that you can have pretty much the same a/f graph with different e-tube and main/air combos. i saw it this past weekend. i do however respectfully completely disagree with your pump jet comments, both in theory and in practice. in theory, the pump jet is mechanical, not hydro-pneumatic, and provides a squirt powered by the thrusting of your foot. it's a split second worth of fuel, and as such cannot possibly effect an a/f *graph* (ie rpm range). in practice, the same pump jet has been in every stage of my car's evolution, from stock 2.4L to street 3.1L to full race engine. in every stage, the car has always had instantaneous throttle response, which i credit to both the torque transfer of our L6s and the capability of the pump circuit. i see no need to change the pump jet. the car falls in its face when you maintain full pedal, NOT when you transition to it. in fact, as the pedal is depressed, the car lurches forward. then promptly chokes for air. you might be right about floats. i haven't looked at mine in years, and its certainly worth looking into again. i find it unlikely to be a fuel supply problem, as i have a high flow/low pressure centrifugal pump that can outflow any realistically possible burn rate. it describes the adjustment, and doesn't offer it as a tuning aid, but rather for us to set it to precise measurements and does not mention application. i suppose we should all verify these adjustments... -mark ps - want some webers again, do you? funny... i'm finally considering ITBs...

thanks for the report, scott. with regards to the f16,

i was re-reading this thread and was surprised that i had already mentioned the costs of large venturis. i must be getting old... i've forgotten my own experience. hah. also, i came across this report about the F-16 emulsion tubes. this furthers my opinion that the F9 is my best-guess. here is a report of the f-16 making an L28 more rich. we want more air, not more fuel!

sigh....

scott - you say you prefer the F16? what others did you try? thanks!

you sir, are 100% correct. i've forgotten about this detail along the way somehow. driveability! he's right... bigger chokes means higher peak hp, but less driveability. i'm running 36mm chokes for the record. weber book wants me at 38-40 for my setup (again, peak hp). think road racing, not autocross or street! i went to the dyno today and i have the graph to back up the effect of big chokes. i brought the most complete jet kit i've ever heard of, and my a/f ratio graph was unfixable. i even had the MAP sensor for advance based on load (or lack thereof) we talked about. helps smooth out the mid-throttle transitions and makes it more driveable, but does NOT help or fix our flat spot. after tuning the car for timing/mixture for peak hp, i then swapped from the [new] F2 emulsion tube back to my [old] F11 tube. all graphs below show the difference, so you can see the effect of this particular swap for yourself. the red plot is the F2 tube, the blue plot is the F11 tube. unfortunately for most, this data is somewhat skewed in that it is tested on 109 octane vp race gas. it's oxygenated, so i run larger jets than i would for normal fuel. that said, here's what the change did: A/F RATIO: as you can see, the ENTIRE curve is richened by this tube. i ran out of dyno time, but when i get a chance for a road test, i will compare the F2 setup to a setup of F11 fitted with (main -5) and (air corrector +10 or +20). i might not be doing this till next summer, but if i remember, i'll post my preference here. TORQUE: preference on these two plots is debatable. for torque plot, I like the F2. POWER: also debatable. i still like the F2 on paper. again, road test of the comparison with proper main/airs is still needed. and if you're interested, here's a video of the dyno run: good luck out there! -mark

went to the dyno today. well john, i'm still running the e31 that jim thompson built for me, and i put down 264hp to the wheels today (dynojet). if your 275 hp statement from yesteryear was talking about from the crank, then i'm pretty damn pleased. hell, i'm damn pleased regardless! this was a 67hp and 64 ft-lb gain from the engine rebuild (forged pistons, race cam, 12:1 compression). this works out to about 34% gain in both hp and ft-lbs for about $5000. you warned me. NA costs $$$. there's still a fair amount of power out there still. my exhaust is still street performance level (msa headers with an open muffler and non-mandrel bent 2.5" pipe). stahl headers and 3" mandrel one day. but more so than that, today i think i finally lost my stubborn attachment to the webers. i have an overwhelmingly complete set of jets, but i can't even come close to getting the a/f ratio reasonably flat. not even close! graphs below. that and according to the weber book my 40dcoes (specifically the 36mm chokes) can't feed what my engine is trying to burn. add that to the tuneablility and driveability equations, and i fell out of love with webers. i still love the nostalgia factor, but... well, that's about it. hah. here are the graphs: A/F RATIO: as you can see its all over the place. the weber sticky has many of us noting this insanely rich dead spot, but not one person has piped in with a cause or solution. so that's cool. i assure you i experimented with mains, idles, air correctors and even got into the weeds with emulsion tubes. this was the best i could do... oh, i even added a MAP (manifold absolute pressure) sensor to add some advance based on load (lack thereof, actually), but no. still falls flat on its face unless you know how to work the pedal. [EDIT -- large chokes. large chokes produce bettter peak hp but poor driveablity. this MUST be what we're seeing here...] TORQUE: and of course this has its effect on the torque. the pedal has to be feathered until above this dead spot (which is now shifted 1k higher thanks to race gas for some reason). this feathering is shown as the relative dip in torque climb as the rpms climb from 3k to 4k. WOT caused the engine to fall flat on its face and sputter and surge in an embarrassing manner. POWER: here's the final power curve, with a feathered throttle input again producing a dip in the climb from 3-4k. (WOT starting at low rpm confused the computer... it thought the user was shifting because of the surge in power/torque). but again, in the end i'm pleased. it sounds and feels very full. here's a video of one of the better dyno runs: lastly, thanks again to all of the experience shared on this thread. it's truly been an eye-opener for me, and based on the number of random "great thread!" comments, your knowledge has been shared with quite a few enthusiasts!

thank you zmanco. i think so too. testing soon! finally got the f2s. although not a night and day difference, there's no question that the car liked the change from f11. the power band seems smoother, almost like a more complete burn. not much a difference (if any) in power, just smoothness and overall driveability throughout the main circuit's rpm range. i did notice a small drop in the flat spot, but it could also be from lower ambient temps giving me more power. damn multi-variables... i bought them from top end, and according to them, any L6 should have them and their selection has nothing to do with displacement per cyl. this contradicts the aforementioned article, but hey. food for thought. my car liked it. perhaps others can report. i'll report on my timing findings when i have them. should receive a MAP (manifold absolute pressure) sensor soon, which will allow my ignition to vary its timing based on load (ie throttle position). hopefully it will help eliminate the dead spot down low. -mark lazeum, your timing seems a little low. i'm by no means an expert, but i believe our cars in general like full advance to be closer to the mid 30s range. my advance is more, but then again, my engine is more radical. i would suggest some dyno time to determine without any doubt what your car wants to see! as for your nose dive it seems all of us have experienced this with the L6 / weber combo. as suggested above it is suspected to be timing based on engine demand. definitely try the f2 emusion tube and see if that clears up your mystery rich condition at 5k. don't confuse the two. the weirdness you mention is our flat spot, not the [accelerator] pump jet / system. (you are 'hitting the gas' at low rpm then doing a dyno run.) this system is a single spurt of extra gas mechanically pushed by your foot when you get on the pedal. it might be a half-second worth of fuel, therefore is not an rpm range. think throttle response, not acceleration. running rich does help combat detonation if you are approaching it, but it does not prevent it. timing and octane do. if you still have a ticking, especially if partial or full load sounds like there are marbles rattling around, then you need to back off your timing or get some better fuel! whenever i heard the warning signs it was under load, not at idle. as for what to work on first idle or main, they are independent of one another and therefore order is of no consequence. the main jet is more important to have right than either the idle or air corrector, but all three are very relevant. get some plus/minus sizes for all three and start experimenting on a dyno or an open road. dyno is best. me, i dyno after significant changes to make sure my timing is right. i of course get mixture too, but seasons change and necessitate changes in jetting. my timing stays untouched after the dyno unless mods require a new baseline (fuel change, compression change, head/cam change, etc). good luck!

when you're right, you're right. cutting the car is currently about as uncomfortable as getting married. reality: each passing week i get closer to the idea of truly cutting the car. and i get closer to getting married. to the car. haha. [still selling carbon fiber body parts, jon? lol.] in all seriousness, thanks for taking the time to lift the fog for me on all points, john. i'll definitely raise the car and soften the struts and report my results here. if there are enough runs, i'd like to experiment with no ARB, too. i do have an event this weekend, but the navy might have other plans for me. here's hoping... speaking of ARB experimentation, is there any problem with simply disconnecting one end of it to simulate no rear bar at all? this would have that effect, right? thanks again to all!

as usual, lots of wonderful responses. thanks to all who are participating. haha. remember how far i went with my engine? that far. no holds barred. (still wondering about cutting the fenders, if i do it will likely be in the subtle z direction... either that or just let the tires stick out.) i do recall when i was installing my camber plates that the bump stops weren't looking new anymore, but rather that they have been bumped a number of times and perhaps should be replaced before too long. i also had to replace a front strut that was completely shot. don't remember if the worn stop was one side or both, but definitely front. i'll report on that. i dont know how tall bump stops normally are, but these are from msa and were about 1.5-2" if my memory serves. is this about normal or is there another type/brand that i should install? i predict i'll find my zip ties all the way at the top this weekend. if so, how can i determine if the blame is spring rate alone, as opposed to ride height or bump stop design? i pulled out my receipts. the front springs are 225s and the rear are 200. as a refresher, tokico illuminas have settings 1-5, with 5 being stiffest. i used to run with the front at a 4 and 3 rear. after putting in camber plates i switched it to 5 front 4 rear, and a few events ago i switched it to 5 and 5. obviously its not working very well for me... tires are kuhmo v710s, 225/50r16. i find the best traction with pressure at 24.5 front and 23.0 rear. please forgive my lack of complete understanding here, but i'm trying! i found and read this thread: http://forums.hybridz.org/showthread.php?t=128079 (Near Zero Front Suspension Droop) the light bulb is slowly beginning to turn on, but is still too dim to be useful! cary, you seem to be voicing a lot about drooping, but after reading the whole thread, i never heard any explanation as to what droop was, and google didn't help either. with regard to limiting droop... sounds wonderful, but droop of WHAT!? haha. do you mean compression of a spring because the car is rolling? i get that drooping is bad, but what *part* physically is drooping? yes, that's *exactly* whats happening! the surging of the car is causing my foot to move, which is trying to be neutral on the pedal, but instead causing the oscillation to worsen unless i back off immediately. the throttle response of our torquey L6s is wonderful, just a tad frustrating with my current setup. checking the strut shaft? do you mean the zip tie test or something else? i thought the over-lowering problem was because of control arm geometry, and not bump stops bottoming out. or is it both? thanks again! -mark

oh and as a reference, here is the car at rest. this was taken the day of the video (this past sunday). i've heard the stern warnings of over-lowering the car, and i did measure to make sure it wasn't below 5" from the ground and that the arms weren't level or below level (forgive the lack of proper terminology!), but i do wonder if it still isn't too low. i also suspect i might have too much camber in rear. and no, i don't have degrees. i've simply been making adjustments between runs (i liked that, didn't like that). i can hold more speed in sweeping turns because of my rear camber, but i think with power i can't afford that camber leaving the apex and for the rest of the course....

here are the most recent pics i have. none of them are ideal, but it's what i have... looking at this first pic again, i'd have to agree with flexicoker in that i'm dead wrong about spinning the outside tire... this clearly shows the inside tire having minimal contact. after this first pic, i decided to reduce my camber (both front and rear) and raise my ride height about a 1/2" or so: the rest are after these changes. ok, so if i'm not mistaken my front springs are 25# stiffer than the rear. i can swap those easily enough. i could also reduce the dampening slightly in the rear, and possibly experiment with no sway bar. thats the in the meantime stuff. sounds like i want to invest in new springs and shocks. recommendations? what does the quaife want to see? (4.37 r180) also, i'm considering (for real this time) ditching these tires and rims and going bigger, possibly entering prepared classes and moving away from DOTs. would going to true slicks change my spring/strut selection? as for rear sway bar, would a smaller sway be more ideal than no rear sway at all? i think stock was 1/2". i'm at 3/4". the throttle quadrant sounds very cool. i did a search or two and found a couple explanations, but my lack of experience requires pictures! hah. is there a thread/tutorial here or anywhere else that could steer me in a better direction? thanks! i'll do the zip tie experiment this weekend... thanks guys!

seems we were both posting at the same time. hmm... dont think its the front. not the bump stops, anyway. the car is quite neutral until i'm at apex and post-apex and either have neutral pedal or attempting to accellerate. then i feel like i'm on ice. grip is being completely lost in the rear, and is due to too much damn torque. perhaps i'll try reducing my rear camber? then again, maybe i'm missing what you're saying entirely. if so, please explain! (i watched the video again and not sure i follow what you're referring to...) the suspension isn't that aggressive. tokico illuminas (all 4 corners on stiffest setting) with 225/200# springs. i do have camber plates. 1" front sway and 3/4" rear. tires are kuhmo v710 225/50r16. theres no question i need a bigger footprint, but i refuse to cut my car (i think! sigh...), and my brakes mandate a minimum 16" rim.

i looked again too, and unfortunately that run didn't have any mistakes in terms of what happens with a touch of too much pedal. if i had to guess, i'd say it was the outer tire that broke loose first, as the car would oversteer. if it were the inner tire, wouldnt it either understeer or be rather unresponsive and/or push? also, my understanding is that the quaiffe biases the power to the outside tire in a turn. that said, the video is what happens if i was being tender with the pedal. if i was being too aggressive, both tires would break loose. this handled a lot more like drifting, whereas the unbalanced tire slippage felt more like on the verge of loosing control. so again, the concern is the pulsing that you hear in the race video. sometimes the pulsing was heard when the tires didnt break loose (or perhaps i didnt feel the slippage?). i interpret this as the suspension oscillating over the road, causing the quaiffe to hunt for the happy power distribution balance. this hunting is what was screwing me, as the torque was surging up and down. if i were pushing grip of the tires, as soon as i hit the slightest bump, the tires would break loose. i understand that this is unavoidable to a certain extent, but i feel like this is happening waayyyy too easily. i intend to experiment with the sway bar next season, but would very much appreciate any input anyone has! thanks!

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shifting this discussion to its own thread: http://forums.hybridz.org/showthread.php?p=956374#post956374

i'm shifting this discussion to a new thread because it was beginning to hijack an engine build thread. i'm not sure if this belongs in the suspension or drivetrain section, but i picked suspension. drivetrain seemed more mechanical than handling, and my questions deal with handling. this is what i posted after autocrossing this past sunday... update-- i finally purchased some of that vp race gas, and man... it makes more of a difference than i had hoped for. i am getting a dramatically more complete (and faster) burn, and it hasn't even been tuned! not at all! i couldn't lay down the power anywhere, which was frustrating, but yet satisfying at the same time. that is, after all, proof that all of the time and money put into my engine has paid off! here's a video from today's race: (note the watch in high quality link) as you may or may not be able to make out, i'm having a hard time with the power, both in terms of keeping the rear end hooked up and taming the beast. i'm really, really having a hard time being smooth. manual steering is a whole lot more varsity now. question for you racers out there... the pulsing of rpms that you hear when i'm under load in a turn and going over a bump (ie the tires sometimes beginning to break loose and me having to be ginger with it)... to me, i think its the result of perhaps not the stiffest suspension (225# springs over illuminas) combined with my quaiffe hunting for where to put the power. in my case, is the quaiffe doing me more harm than good, or is this just the challenge of having more power than you can use? (if in the case the answer isn't so simple, i'll shift this to a new thread) thanks!

by the way, jon... although that fuel claim from the VP expert (gain of 6%) is untested by dyno numbers, i am here to say that it *feels* like more! the reason is that this crazy fuel burns no matter what. my mixture is bad, my timing is a stab in the dark, but it burned faster and more complete than ever. i had power down low when it used to just bog until the cam kicked in. so, my report is that this fuel really is all that. however... the price is about $14 a gallon AND the mpg is worse because of density and oxygenation reasons. financially worth it? absolutely not. but somehow its well worth it and i doubt i will look back. who knew?

yeah, i was afraid of that. hopefully johnc will pipe in, too. i still intend to experiment with no rear sway... but that will have to wait till next season. uh... i couldn't floor it *anywhere.* in the turns, the tires were breaking loose at like 1/2" of pedal (or so it seemed with the adrenaline!). driving my Z now requires a level of finesse i don't yet have. it was all i could do to keep the car neutral in a turn and NOT break the tires loose. keep in mind this video was my best run, so this was the most finesse i was able to muster. it might as well be 600hp or some other obscene number, because i feel like i cant use it. (60 degree temps didnt help the traction dept, either) if it sounds like i'm exaggerating, i don't blame you. that pedal was waaay too touchy today. i have no doubt the dyno will back up my claim. how does that saying go? you reap what you sow... curses! my track times (relative to my competitors) are going down because its now so much more difficult to drive smoothly. and by that i mean its soooo much more fun...