Tony D
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Posts posted by Tony D
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That's the mechanical end, here's the source for the electronics:
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The MAP reading on an ITB setup is not from the plenum...
Lag is a function of the turbo flow, changing the plenum does nothing to change the flow, so 'lag' may be a way to describe it, but 'drivability' is also a prime consideration. If you have 150HP at 3000 rpms, and 600 at 3400, driving that car may be slightly difficult in normal day-to-day situations.
Similarly, if your MAP goes positive EVERY time your foot caresses the throttle pedal, your gas mileage goes to sh*t. In that case, a larger plenum will work as the appropriate accumulator allowing some 'lag' between partial throttle applications and manifold boosting.
I hesitate STRONGLY to say it's 'lag' simply because of the negative connotations related to it, and because of generally the 'lag' everybody is talking about is from a WOT application, and NOT from a partial-throttle application. Generally lag is the time it takes to build FULL BOOST after WOT is initiated ABOVE 'boost threshold'----'lag' is not something associated to partial throttle applications.
In partial throttle applications, you most definately DO NOT want boost happening instantaneously (which is an indication of improper plenum sizing in both ITB and single throttle body applications). There has to be some deadband in the throttle pedal application where boost does not occur, or you will have fuel economy that is terrible.
The question you asked was two different things, and unrelated, so on the face of it, "NO and NO"----it's not an 'either or' situation.
The key on carburetted applications is to have MORE deadband than you do with an EFI setup as the carburettor just doesn't function well at '0' manifold vacuum, while EFI can operate there easily. The problem with Carbs is transitional leans, and if you undersized the plenum, you hit those points all the time, and get lean pop on cruise. As a result a larger plenum gives you more useable throttle play without boosting. You could always go with a larger turbine and have the same effect...but at the expense of spooling at higher rpms, meaning your boost threshold is higher, and you have less of a useable rpm range.
Which do you want more? Driveability and the ability to make 17 psi at 1700 rpms, and pull to 6000, or Drivability and the ability to make 17psi at 3400rpms, and pull to 6500? I know which setup I chose, and it was FAR better with a smaller turbo spooling at a lower rpm than a larger turbo spooling at a higher rpm.
The discussions should really be separate: Carburettors and EFI. They are so totally different when tuning plenum sizing and other variables if you try to apply one to another you will end up seriously confused.
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"Yes..believe it or not, I knew at some stage I was going to build a fire breathing L motor so started buying parts here and there over the years."
I started that process in 1985....I'm almost complete with the bits.
The 350HP blowthrough setup was just something 'to get me through till I get all the good parts', now 40K+ miles later I'm still not around to it, but then again, other things are getting in the way...like the 80 foot pine tree that blew over in my front yard last night...dammit!
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You go onto boost mapping with the slightest touch of the pedal due to insufficient plenum volume. The Centrifugal compressor will overfeed the reciprocating compressor (engine) really quickly. It's why they put such large receivers on screw and centrifugal compressors (suction bottles is another name for them) when feeding a reciprocating booster compressor.
As a result of the instant boosting in the manifold, you end up running in a 12:1 mapping, instead of something more conservative. Your mileage goes to hell... Now, if you put a much larger turbine section on, so it's slightly laggier you may restore the balance of NA cruising, but it kind of defeats the idea of having a turbine optimized for response. With a larger plenum, small throttle excursions will not result in the increased flow causing a bump to say 3psi instead of '0'.... In a megasquirt the difference in sized can be seen as a jump almost instantly from a 54kpa cruise to 108 or 110kpa instead of from 54 to 80kpa with the larger plenum. The only thing changed in the test was the plenum. I haven't had much time to play with the new setups and datalog everything to see what kind of numbers I get and relate them to what was seen on the same setups with carbs instead of ITBs.
Also I note the BOV tuning has to be retweaked due to the plenum change. The blowoff action is much harsher on the smaller plenum from what I can hear.
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The Coates spherical valve will require a new head for optimization, and JeffP called and they weren't interested in anything other than conversions of diesels in city busses, regardless of who paid development costs. Coates spherical valve conversions of Diesels to CNG in busses has been done for years. As I said then, working for the company that was supplying the CNG for the Busses and having an onsite Cat Rep fulltime in our corporate offices held no sway with the Coates People.
The DEVAS system would use the stock head, remove the valve cover and all drive components (unless you wanted to drive the pump from the camshaft gear...but I would think retrofitting the Diesel front cover and driving the pump in the same way the diesel injection pump is driven would be an easy swap and use a lot of stock components.) bolt a plate on with your hydraulic actuators, and go from there. The DEVAS system could fit on just about any engine head, the actuators are not that big.
But yeah, from a practical standpoint, a poppett valve is far more practical than the spherical valve. I would love to have the spherical valve...BUT the timing is not variable, and duration is not variable, etc etc etc... The spherical valve would be great for a FIXED camshaft profile. But the DEVAS allows infinitely adjustable cam profile and timing. Think VTEC with variable lift... It really ends up being far superior in regards to drivability and versatility when you think about the Coates design in that it's really nothing more than a fixed cam profile. It's just flowing so much more because of less restriction. But it's not adjustable, so for fuel economy AND power, it will suffer the same as a conventional camshaft.
I had a rotary valve on my 360CC Suzuki Jeep from 1976............
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One barrel maybe would use a linear response. If you have multiple barrels, then you want a dead tip-in for drivability.
Why put anything at all in there or worry about designing the 'correct cam' for the application, and simply control the intake and exhaust valves via electrohydraulic actuators driven off an engine-based pump and accumulator setup? Variable valve lift, timing, and duration will give you EXACTLY the same response as a throttle valve without anything there to muck up the flow. And you can bet the advantages of variable valve events will make more power everywhere along the powerband as lift/duration/rpm is all optimized for each point on the curve, infinately recalculated realtime as the engine is being driven! Twin 140MHz ECU processors will do that easily on a 12Cylinder engine to 12K rpms I believe.
"DEVAS"
(Since we're throwing the stuff out there...)
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Jeff,
That is what many of the higher horsepower cars started doing with OER's since they have a separate vent for the float bowl. Like SHOZ's diagram, taking the pressure from say the Torus of the Turbo (or S/C) and ducting it directly to the float bowl is an option. You will then tune on-boost enrichment via the bleeder or fixed orifice size.
What ended up happening was on twin turbo cars with really high HP, the two holes in the stock HKS plenum was over-richening the mix. Rather than enlarging the plenum holes and rebolting it, they took out the divider wall, or made the holes quite a bit bigger so it was not creating as much of a pressure differential, and then vented externally.
The two holes in the plenum will be a flow restriction at higher HP levels, so they eliminated them as it was easier to change the venting externally.
As I mention, though, neither the Cartech, nor many of the 4X4 boxes I see incorporate that enrichment feature. And on 2X4 box with the A.R I was running, I went immediately to boost on slight throttle application at highway cruise, and was at 0 manifold vacuum cruising. On the HKS plenum I was slightly negative, and slight throttle applications didn't make be go positive.
On an EFI car, things would be different as tuning is usually MAP based. Then the only thing you notice is your fuel mileage goes to hell compared to a larger plenum....
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Yepo carbs are alot smoother on the dyno but I noticed that smoothing was set to 5 which is alot high for my taste. I prefer to have it lower say 3 so you can see the bumpiness. That way you can tell if you have too much timing before you can hear it.
You mean on the Dyno Setting, right? That is a very good point. I was making mention since we ran the same settings when we dynoed our Bonneville Engine and with the same settings you could see more 'bumpieness' than with the Webers.
But that is a very good point, many people don't ask about the smooting and interpolation settings of the dyno, and don't really see what their car is doing during tuning. Keep it fast-responding while tuning, and "Just up the smoothing for the final run you post on the internet" LOL:icon45:
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I was told the cast pistons were sufficient for my application.
With all the money you are putting into an engine, what is the realistic price differential between a set of NEW (not new-to-me) cast pistons, and a set of NEW Forged Slugs? At 89mm that sounds a lot like a Chevy Bore Size....
Keep an open mind on parts sourcing, and realize that Buick Pistons fit in a Chevy same as Chevy Pistons do... Parts is parts. In the 'old days' people were buying stock Chevy 2300 Vega Pistons because you got them for CHEAP, with rings, and they were forged (keeping with the aluminum block and special lining expansion rates). They were a popular 3L engine piston option, and anything for a Chevy is an order of magnitude cheaper than something with 'Datsun' tagged on it. In many cases you could buy a SET of TRW Aftermarket Forged Slugs cheaper than a set of new cast stock pistons!
Other than some more noise (overblown IMO) and possibly some more oil consumption (again, not an issue for me) Forged Pistons will afford you a bottom end that doesn't need to be attended to if you suddenly realize that stopping the rush at 7000rpms is just a drag.
For me, with the costs of parts, the differential in piston costs doesn't make much sense to not spend a couple of hundred more for forged and be done with it. It's not like they will last less long eh?
That is what I was getting at.
And I like the VH 45 Turbo Idea. Mmmmmmmmm Turbo.....LOL
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Glad to do it. I'm always interested in finding out 'old school' forensics!
Would make an interesting bit of facts to post as well.
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You have to read my third paragraph closely, I thought I was specifying "Degrees F" in each of the temperatures, but apparently did only in paragraph three.
It was a BIG 'off day' yesterday, sent e-mails out with references to attachments that I didn't attach, now this... Man, I'm slippin'...bad!
>:^(
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On a side note, the current jetting will probably be spot on come spring around here.
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Nice numbers, that is a strong car. I always liked the 'sharpie on the sheet' look to a Weber Dyno Curve. Not the jaggies found on some EFI systems. Then again, they don't vary with the season. Give sumpthin', get sumpthin'!
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Curiously, the last drawing Braap put up looks a lot like the inside of the old HKS Type-1 Turbo Surge Tank. The smaller upper plenum was what was vented to the float bowl, and there were two metered orifices that bled pressure into the larger plenum between the ITB Pairs at 3&4, and 5&6.
I haven't looked at the Type 2 Plenum closely, I got it and shelved it due to other jobs in progress (24 Hours of Lemons, anyone?) so I can check it in a couple of weeks to see how it compares. I know it has a similar plenum division, but is done differently than their Type 1 Plenums.
Jeff, would you want to take a look at those old 80's Tech HKS Plenums in person? I could probably make my way your direction if you're interested in taking some dimensions. It would be interesting to see the CFD comparisons for 80's technology...
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"I figured out that I can buy a GM-Performance crate motor for roughly the same amount it would cost to build a ~decent~ L-series. The GM engine comes with a warranty and ready-to-ship replacements. The bonus is that the GM motor will put out as much power as TWO L-series motors."
Curiously that is exactly what many of the 'NASCAR EXPERIENCE' style driving schools use! The one where I was working used ZZ4 Crate Motors with a Big Block Oil Pump in a Winston West Chassis. If the motor blew, GM covered it under warranty (really!) SO as a result the engine costs through a season were virtually nil. It really is a smart move for people who will be racing.
I didn't see the quote as out of line, but for KA24 pistons in the engine, you are overbuying the machine work AND the shop! If you are running cast pistons, go to a local machine shop that has a reputation as a competent general purpose machine shop and get your machine work done there, and as you said Assemble Yourself.
Going back to my VW days, and my old standby Gene Berg, he would adamantly suggest you do all the engine assembly work yourself. He was the first to say there is nothing special about it, and if you do it you know what was done. If you really really really pushed, they would assemble the engine for you, but generally this was not the way they did business. The money for assembly is in the HEAD, not the block. Have the HEAD prepped/ported/assembled by a specialist shop, but the block can be done at home with a few specialized tools and care at home.
Buy the "How to Modify" book, and have at it. The bottom end is fairly straightforward if you take your time, follow the recommendations, and have the tools to do it.
Yes, TimZ, I noticed that as well! If it's not a serious build, then don't spend the serious money. It's a waste with cast pistons, no reason not to do it yourself with cast slugs and a 6500 rpms rev limit...
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My Megasquirt is logging a 15-20 degree difference between the thermostat location and the CHTS at the same time. That's saying it gets to temperature faster than at the thermostat location.
If I start the car, it will show 100 at the thermostat, while the CHTS is showing 100, quickly thereafter I will see 115/120 at the CHTS while the thermostat is still at 100.
If it let it sit there at idle for a while the differential will rarley exceed 5 degrees F. So from a static standpoint, they are 'identical' temperatures.
BUT....
When I go out and actually drive the car, I will see a temperature change on the CHTS almost immediately, whereas the Thermostat mounted location will lag for a significant time. If under sustained load, eventually the temperature will stabilize to within the 5-10 degree difference between CHTS and Thermostat, but under quick loads, I have seen the difference be as much at 20 to 25 degrees.
My thinking is the CHTS location is a more quickly responding location than the thermostat. Under loads it seems to rise faster and to higher numbers than what the T-Stat location seems to show.
I'd be curious to see if you can duplicate my testing results independently.
I can see how a localized hot-spot can cause detonation issues, and that putting the sensor there would 'safe' the whole engine based on hottest-spot sensing. Everywhere in the world got a thermostat housing mounted sensor, but for some reason we got a CHTS with the same sensing resistance pairs... I think they had an issue with Federal Emissions, and needed a more precise control of hot-spot sensing like for leaning out / egr mapping. As a result the relocated the sensor. This plays well for guys with turbos as you want the same sort of quick response.
Anyway, that was the long form of the 'yes there is a difference in the temperatures, the CHTS responds quicker with higher peaks in the read temps than the thermostat location'.
I guess you are happy you didn't use a metal gasket and blow your piston in #5 about now, eh? Look on the bright side, because that is it! Get your tuning down, and THEN seal it hard.
Till then, use your head gasket as your safety valve. You don't want to sink any ring lands on those pistons!!!
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Blast from the past! That is an 80's era Electronic Fuel Injection setup. Analog fuel computer...SK made them as well. They used double stock injectors as that was all that was available at the time, and with the pulsewidth control it got hairy to get anything idling. The second stage of injectors was set to come on after 2500rpms, just before the engine starts getting on the torque curve.
For some Megasquirt applications with a dual-table setup it would be killer...
BTW, they are 'OER' Aftermarket Throttle Bodies. Wickedbitchencool that it comes with the OEM Installation Manual!
If I didn't already have a set of HKS ITB's from similar vintage, I'd be sorely tempted to bid on them for the price they are currently sitting at! That setup would work nicely at Bonneville. They are 50mm Bodies, that is some HEAVY flow!
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Is the back end subframe mounted like the S130 or Z32? If so, one of more of the big bushings that mount to the unitbody may be deflecting due to damage or wear. Whole back end can move around and send you off in all sorts of directions under power.
If you had wrinklewalls, that would be different...JeffP's car wants to change lanes when he romps it...flexy sidewalls do that...
Good Luck! Keep us posted on what you find!!!
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Yeah, that's the lighter option! LOL
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32 valve pushrod heads have been available for SB Chevies for years.
Detroit Diesels ran a four valve head with bridged valves off pushrods, and that was a two stroke! LOL
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Just blank the mounting face, allowing final machining to suit the end user.
As for TWM throttle bodies, most ITB's use the standard Weber/Mikuini/Solex/OER/Dellorto inlet side carburettor flange dimensions, so it should be universal.
I don't know if the TWM manifold makes any radical departure on bore spacing of the pairs either. My Cannon Manifold used the same ITG filter base with 40mm Webers as my Mikuini 44's on a Mikuini Manifold, as did the Dellortos on the JDM manifold. So that issue may well be a non-starter.
I think the biggest difference on the manifolds is length, and mounting height. Cannon/JDM/TWM seem to be straight out from the head, while the Mikuini mounts the carb bodies notably higher above the headers. TimZ has some good photos of this in some of his older posts.
My HKS ITB's have the same mounting surface print as my Mikuini 44's, so if that's any indicator the manifold would be a 'universal part' the only caveat being hood clearance on a Mikuini-Manifolded Car.
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Will the fuel/brake lines have a 'scatter cover' where they pass through the plane of rotation of the flywheel?
I don't know if that's required by class or not. Ususally a 1/4" plate suffices, and you can make it look decent without too much effort.
Kudos for getting it in the car and looking great. Inspires me to get out there and do my 73 at long last...
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Yoyoyo, finally got my tuning polished up enough that I think I can post it up.
Bone stock n47 L28. Yeah baby.
MS1 with 2.2 board running fuel only.
:EDIT copied in rest of info by mobythevan:
Mine? Stock: injectors, everything... Think they are 195cc..?
What else might you want to know?
Oh and 240sx TPS, think thats the same as the ZX.
Injector open - 1.0 ms
Voltage Correction - .1 ms/V
I want to confirm for anyone wondering, I plugged Gavin's numbers into a stock 280Z that we are prepping for the 24 Hours of Lemons at Thunderhill the end of this month, and the car fired and ran well. Burned 'em leaving the line and good scratch in second gear as well! So for an 'out of the box I HAVE to drive this RIGHT NOW' plug-and-play 8X8 set of N/A tables I will say they worked.
My differences (which attest to Gavin's Map) I have O2 correction disabled, so it's running ONLY on his map.
My Req Fuel is something like 18.6 or thereabouts, only because I used 170CC injectors (which I thought were stock), this should be of no consequence.
WE currently have the accel bins and cold start enrichment 'off' for all intents and purposes because we wanted to test his MAP, and not how well anyting was masked. I will post back as we install the rest of this supplementary enrichments on his original post, but I know there are people looking for 'confirmation' that one set of tables works well or not.
I say Gavin's is a great table for someone who needs to drive the car right after installation. Chances are good we will be runnning his fueling table for the race, unaltered.
Thanks for posting, Gavin.
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Having disassembled several 280Z's this past month (particularly the front ends) I would be curious as to the effect the larger bumpers, turn signal relocation, and little winglets behind the bumper all have on the flow on the front of the car 280Z versus 240Z.
From the data Nissan used, they referenced 'the prior model' in the S130 literature, but their diagrams show a 240Z.
I have gotten curious as to the aero difference between an all stock 240 with the skinny bumper, versus the 77/78 models with the big bumpers and all the other radiator opening blocking items (bumper, turn signals, turn signal mounting brackets, etc).
Being that last word I got was 'the rules will be rewritten in this off season' I'm having a bad feeling that our Bonneville effort will not be reproduced with a G-Nose on the car, but with full 77/78 280Z factory dress. And I'm not loving the thought of sourcing new bumper rubbers...saved two sets, but the $$$ on E-Bay people get for them is making it cheaper to run a G-Nose!
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I believe 1 Fast Z is running a copper head gasket on his DOHC Conversion, as well as his 3.1 Stroker.
I also believe he said he can source them for customers.
"Search, the Truth is out there!"
Stroker Sticker Shock
in Nissan L6 Forum
Posted
Crank looks lightened slightly on the extreme counterwieght ends, but doesn't resemble any 'knife edged cranks' I have seen in the past.
Does look like pistons/rods are aftermarket from the photos.