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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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Discussion Starter · #22 ·
So I have a block out for darton sleeve, i also came upon a y8 head that was entirely stock, ~ 220k miles, from the scrap yard, I ported that in case I can't find a suitable 3 stage head, I figure the swirl effect along with a custom cam will make it work in a pinch. so far i have the z6 block, d17a2 crank, d16 eagle rods (narrowed for d17 crank), wiseco d17 forged pistons(-14.4cc) a ac log type manifold, 660cc e85 compliant injectors, 225lph e85 compliant fuel pump, aeromotive rising rate fpr, smanager tuning with hondata v3 chip, wideband o2 sensor and associated gauges and electronics.
Hoping to get the Thompson stroke motor to testing/ carb compliant by early 2022.
It should be noted at this point that I'm after average mpg for MY commute. NOT power or MAX torque, just an easy to drive efficient DD that can hold its own.
As I am in CA the emissions test will end up deciding if im legal or not, so I plan on a recirculating pcv system, gapless top ring, balancing, ect, to provide the best possible atomization for each cam profile, which Intake i use will depend on which(b7, z6,y8) manifold atomizes best with the afore mentioned modifications.
I have roughly 14 months to complete planning and building or I default to another mildly built z6, which ain't bad, but for a gearhead leaves a bit to be desired .
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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Discussion Starter · #25 ·
I had to use my pistons on a customer build, and am now playing with the idea of a 78mm sleeve and $1200 pistons, talk me out of it before I do something stupid please🤪
 

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Sloppy Jalopy
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I had to use my pistons on a customer build, and am now playing with the idea of a 78mm sleeve and $1200 pistons, talk me out of it before I do something stupid please🤪
but why
 

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Sloppy Jalopy
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Cause I'm seriously thinking of raiding my daughters college fund, lol. And I'm pretty sure my wife will kill me.
do it! but not such a big bore ,,,
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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Discussion Starter · #32 ·
So the wisco's went into a pretty cool 04 build, but the tip was enough(we exceeded whp and 1/8 mile ets by 26 whp and .23 sec) to cover a set of custom pistons from SRP, I had to call in a few favors and lock in a build, but gapless top ring, moly faced 2nd, stainless oil with supposedly the best expansion ring design for forced induction. Did I mention a .002 deck clearance with 137mm rods? 10.2:1 compression with the y8 head, or 9.8:1 with z6/z7 head, thats static cr. Currently mapping out cam profiles for a 1.7-1.5 y8/z6 and a 1.7/1.5/1.3 for the z7 3 stage (though getting it to engage the right lobes is going to be trickery for sure).
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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Discussion Starter · #33 ·
So for dynamic cr on z6/y8 build it would be 8.90:1/9.22:1 on vtec lobe. For z7 build it would be 8.90:1 4 valve mode and 8.2:1 on high lobe. this is provided I can rig a way for 3 valve mode to run reg cam, 4 valve mode to run Thompson de-stroking to 1.5 and high to run 1.3 respectively.
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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Discussion Starter · #34 ·
I'm thinking a 5 psi switch over for z6 or y8 build, and a boost cut of 16 psi for z6 or 13 psi for y8, if this cam bearing thing pans out and I can use one of these 3 stage heads probably a 3 psi switch to 4v mode and a 10 psi switch to high mode. Im hoping these things will keep torque delivery flat and super predictable, reduce side stresses from the huge 1.7 stroke at higher rpms, and allow for greater smog tunabillty as the designs progress, there will ALWAYS be a space in my heart and a spot on my calendar to keep the dd D alive.
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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Discussion Starter · #37 ·
That I'm not really sure, my experience with roots and vane type chargers and Thompson stroke cams showed a 30% increase in fuel economy, and those were carburated engines with pretty basic ignition controls compared to what can be done easily with a D.
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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Discussion Starter · #38 ·
So any way I work the pins on the z7 2 stage vtec setup I can't get it to work a 2 lobe Thompson stroke without a $6800 set of custom cnc'ed rockers, unless im missing something that's probably very obvious, I just need 4.3 more mm to make it work and not break after 1 pull if not in the middle of warming up.
This project has been shelved for a while as I slowly made a rough draft of what would be required to make it work and wait for an estimate from a friend on the machine side of it.
So now I know it's out of reach I'll be using a spare y8 or z6 head, came upon a stash of good oem cam cores, mostly y8 but there was an a6, b2 lx auto, and 3, yes 3 z6 cams, so I may try a couple different grinds to see how much destroking it can take and still be fun to drive.
At this point I've had to use most everything I had piled up aside from the rods and crank, but I have lots of unpreped decent to good short blocks lying around just waiting on me to get my :poop: together and clear my list so I can get to the fun stuff.
 

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I've had this page open for probably 6 months and just looked at it again to see the update. Ive never heard of the something like this except for this thread and its had my attention for a while. What is the 4.3mm difference in the rockers and where does it need to be adjusted?
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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Discussion Starter · #40 ·
I've had this page open for probably 6 months and just looked at it again to see the update. Ive never heard of the something like this except for this thread and its had my attention for a while. What is the 4.3mm difference in the rockers and where does it need to be adjusted?
I'm actually trying to breathe new life into an old concept, Thompson stoke engines were first designed in the 60s with roots and vane type supercharges capable of boost at low rpm, and were actually decently efficient, Ford had a falcon interceptor model that used a 265cu in v8 and thats where I got my first taste nearly 20 years ago.
As for the rocker question I need more space for the vtec pins to move around in so I can cut pin length down, add an extra pin enabling use of a single valve in vacuum switching to 2 valve on a mild Thompson lobe at low boost, then activating the vtec lobe for a more drastic Thompson lobe at higher boost levels. this would essentially allow the motor to run as a 12 valve 1.7l with a compression ratio of 10.6:1 at low loads, a 16 valve 1.5l with something like 9.4:1 compression at low boost levels and a 1.3l with 8.1:1 at higher boost levels. As the intake valve hangs open longer you get reduced compression losses, makes it easier for the piston on the power stroke to push the piston on the compression stroke up, resulting in more torque, and better economy than most boosted engines because the volume of air being pushed back into the manifold at the beginning of the compression stroke while the valves are still open tends to atomize the fuel exceptionally well, while also reducing the actual volume of air being used.
 
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