Xnke
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Posts posted by Xnke
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MAT heat soak could be a problem; the MAT is in the main plenum assembly. I've removed the supercharger charge piping and am doing tests using a 38mm throttle body (it's just a test!) stuffed into the plenum coupler this afternoon, trying to at least get the car to idle properly and return to idle. I've tried the dual-throttle setup before and it worked fine...but was such a pain that I removed it, trying to keep thing simpler.
If I have to run two throttles, that's fine...Miata guys do it regularly, with very similarly placed superchargers...That's actually where i got the idea that this might just work from.
The idle MAP and VE ARE sky-high. I don't have a clue why.
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I think you spent the money in the wrong place!
Headwork if you wanna see the big numbers...it can't breath past 4000RPM, and even at 4K you'd want to se 200+ft-lbs!
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Use the stock copper and you'll never overheat.
Use a thin aluminum one and watch the problems come up!
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What car is the transmission from?
240SX will bolt directly up, but will be clocked WAYYY off. Z22/24 from a truck or 200SX will be clocked wrong by 15* or so.
You may have a Z-series transmission...engine is tilted differently, but the bellhousing bolt pattern and dowel pins will line up between all three engine families.
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So we've progressed from won't idle under 1500RPM to will idle at 750RPM...but strangely.
New camshaft, got all the bugs worked out with that, engine still idles high and runs very well from 2000RPM and up. Same as before...so time to fix the idle.
Started working the idle down a little at a time, got it to go along at 1000RPM. That's acceptable to start working up again. Shut the fully warmed up car off, coolant temp 190F, IAT 100F, supercharger belt slipping a little so time to re-tension (new belt).
Re-tensioned belt, fire the car back up, coolant temp now 140F. Car fires right off, idles at 750RPM VERY rough. Wideband shows VERY lean. Start richening up the idle, to get idle AFR's to 13.8-14:1, and the table values skyrocket...idles very pretty at 750RPM and 90-93VE. Stable idle...pedaling the throttle revs poorly, going lean as RPM's climb, but returns to 750RPM reliably.
Turn car off, go to check for stupidity that I might have left under the hood.
Come back, fire up the car...have to kick the pedal and get the revs to 2000RPM and it'll idle at 50-53VE at 13.8:1 AFR, again, perfectly stable but revs decently now. Idle will NOT drop below 2000 without dying, unless I choke it by smothering it with my hand...then it drops and will idle at 750, again, stable, but up in the 90-93VE range, and won't rev over 2000RPM.
You know, it'd be really awesome if I was trying to build a possessed car, but it's getting old now.
Has anyone had an EDIS module do silly stuff like this? I'm starting to think it's ignition based, as this is the third different set of injectors, both injector drivers have been rebuilt because one of them acted funny after I used some very bad injector settings, and I've calibrated and checked the wideband sensor in two different cars to make sure it's not causing the problem.
MSQ and two datalogs, one is a very strange 400RPM idle that would NOT rev at all, the other is the strange 750RPM idle. Can anyone find anything really wrong here? Firmware is 3.3.1a, re-flashed it this morning before i started working on the car to eliminate bad firmware causing strangeness.Drop the ".zip" extensions when you get the file, they're only on there to allow it to be added to the post. The files are not compressed or anything.
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You can bend a dogleg in it, but it will shorten up the arm and up your boost pressure.
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Not to mention that if you DO get 700HP in an S30, you won't drive it on the street...
It's not an old american muscle car, there is NO room to bolt in the safety cage you'll need/want and be able to get away without wearing a helmet and gloves everywhere you drive it. To not wear the helmet and gloves is to invite instant death the first time you screw up.
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I've sent along a PM with some relavent information; along with some links to photo-filled threads to show you some about the cooling aspects that need to be addressed. Also, Honsowetz's book. Get it, just for the photos...alot of the actual information in the book is wrong/erroneous.
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You don't see it done in the US much because more than 450hp starts costing cubid dollars. The first 450hp is very cheap.
The problem isn't blocks or rods or heads or cams, nor manifolds or turbos. those problems can all be solved with money. The problems show up in the details, in heat, and in tuning.
Nobody wants to spend the money doing the hard work...they all want to cram 35+lbs of boost on methanol/water injection with shiny intakes, big turbos, stock ports and mild cams, expecting big power because the 4-valve Hondas and Toyotas can do it till the rod bearings go.
I will state that you need less than 28lbs of boost to make 700hp.
And you can hold it at peak power for 5 to 10 minutes at a time at that level...north of 1100 was done here in the 80s, and more than that has been done in Japan and Australia.
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Suit yourself. Study up on the existing 700hp+ l28s in existance.
I have, I know what it took others, and I know that you'll ignore it and break many engines before you either give up and do it right, or say it can't be done and move on.
Best of luck with your build.
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What makes you think you need 700hp? Do you need to put an S130 in full street trim into the 9's?
Are we building an L for a Cedric? If so, that's somewhat more reasonable...
To hit your marks, consider bore strength, heat transfer, and airflow management before you start into the money. The stock rods and crank will hold that with minimal prep, the stock pistons will show their true colors about 450hp.
You need some stronger, lighter pistons, and you need to prep the cylinder head and intake manifold to your airflow needs. To make 700 boosted wheel horsepower, you are looking at building a 350hp N/A engine...which is fine and can be done. You will probably be in 10kusd or a little over, then you will need to consider the transmission and structure of the car body.
The stock intake can do it...but that doesn't make it the best way to go. You can do it under 7500rpm...which might be, depending on your transmission.
Get the head worked by the best in the business, get a cam fitted that fits the head flow, and match your intake to the flow needs. Prioritize equality over massive flow...if runners 2-5 flow 250cfm, but 1 and 6 only move 180...then an intake that flows 200cfm on all six will make more reliable power.
I'm interested to hear what chassis this is going in, as well as the transmission plan before I speculate on how I would approach this.
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Hit it with copper rtv on the exhaust side and torque properly and you will have no problems...copper spray I have never had work for me, but the rtv works on the head flange.
Improper torque will let it burn out no matter what sealant you use.
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Not running the carbs in series, but two seperate T fittings, and you haven't hooked the float bowl vents up to anything, right?
Adjust your fuel pressure regulator to produce 3-4PSI of fuel pressure.
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Again, why? It's totally not needed unless you just want to run a custom flywheel...
The diesel crank is the same length and mounts up the same as the stock crankshaft, just with a longer stroke.
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So you are plumbed as follows?
Fuel pump-->feedline--->Tee off to carb 1--->Tee off to carb 2--->regulator---->return to tank
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The engine doesn't seem to be assembled...and with the crank work done there will be a custom flywheel or some clutch fiddling required.
This post seems like someone trying to skirt the rules of the for-sale section, more than anything else.
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The larger the piston diameter, the better...to a point. It allows better valve motion and unshrouding, allows a lower cylinder pressure to exert the same force, but at the same time becomes more detonation prone...all of this is generalization but you get the idea of what you're balancing here.
With no headwork at all, an 87mm bore does well. 86mm does just fine too, but once you get to 88mm and beyond you're really just spending money if you're not starting to pull in the chamber shape and valve placement into the picture.
The L24 rods on the diesel crank are used to make a commonly available piston workable...the difference in rod/stroke and bore/rod ratios aren't world-shifting, so unless you've already planned on and aquired the right parts, don't worry about it.
If you're not doing any port or chamber work, going over 0.460" lift isn't really beneficial, IMO. Exceeding 280* of seat duration tends to make things soggy under about 2000RPM, but from 2500-6500 most cams of that spec will rev nicely.
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40's are too small for an L28...they're only just big enough for an L24, really.
Any L on 40's will make more power with little to absolutely no difference in drivability with 45's, assuming both are properly tuned and the choke sizes are correct.
ITB throttles should be approximately 80% the size of a single throttle plate for a given engine, and engines that breath well can use throttles up to 95%.
Either way, they'll work...just one will make more power than the other for little to no difference in cost or drivability.
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I'd skip the schneider cam and get something bigger, but that's just me. Look into Delta cams regrinds or Isky regrinds, and don't count on your lash pads being a certain size till you have the cam and your refinished rockers in hand, and the valve job has been done.
Look for a cam with a 64-68 degree intake closing point, if you are going to run flat top pistons and an N42 chamber. it will help with any possible detonation issues you might have.
If running carbs, the stock SU carbs can be quite nice if they are in very good condition, if not, then triple Mikuni PHH44s are very responsive, as are Weber DCOE45s. both will need to be tuned appropriately but will reward you with snappy throttle response and a harmonious sound.
Look for a header with 1 5/8 primary tubes, with your final merge 28 to 36 inches from the back of the valve. Be sure to fit an M18x1.5 threaded bung in there after the final merge, just plug it if you need, but it will be needed if you want to run a wideband O2 sensor to assist on your tuning.
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Just for reference, for a slightly lowered Z on 210lb/in springs, what would a good damper be these days? Bilstein P-0032's arent available currently, and I've been considering the tokico HP Blues, as they are still available (listed as such, anyway) from some of datsun places.
Would the KYBs or Monroes (only the OE replacement are available) handle the heavier spring rates?
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I can do the repair, but it simply isn't worth it.
ANY 240SX transmission will physically fit, but will be 2" longer. They also only got stronger the newer the box gets.
If you have the gearshift stick from the trans you bought, it'll work fine save for the weird plate welded on the top of the case...that's certainly not standard there...
The shifter will be sloppier than the original, but the gearset isn't any different.
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Si valve makes the Nissan Competition valves...they are stainless, swirl polished, and oversize.
Altogether unneeded unless you are getting the head ported, and there isn't room to idealize the intake valve anyway.
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Tecretta, I may be interested...I use the Z car flat tops as well.
He's talking about SSS 4-cylinder flat tops...not Z flat tops.
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P90 and P79 valves are 2mm shorter than earlier valves. Currently they are not readily available...read that as custom valves.
A 45mm intake and a 36.5mm exhaust can be fitted in most heads on the original seats. Unless you are getting the head ported, are converting to a solid rocker post and aftermarket camshaft, and are going to adjust the valve sizes to suit your engine, it is not productive.
If you are getting the head ported, then consider the expense incurred in setting up the rest of the head and valvetrain, before spending the money on custom valves that may actually hinder flow, depending on sizing and placement.
Strange problems with engine control
in MegaSquirt
Posted
Idle MAP is still high, but not so bad as it was.
I removed the supercharger charge piping and fitted a 38mm throttle body backwards stuffed into the 2.25" coupler on the front of the intake.
The result?
VERY reasonable 800RPM idle...with a damned rowdy cam. A perfectly drivable (although completely illegal...I had a throttle cable coming up through the hole in the hood into the open window...) 950RPM idle...which was the initial target. Battery corrections need help, as when the electric fans kick on it nearly stalls, but now I know the root cause of the engine that wouldn't return to idle.
The MASSIVE plenum volume. If I reduce the plenum volume, the engine runs semi-normally. This means, unfortunately, the double-throttle setup will have to return...blagh.