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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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Discussion Starter · #1 ·
If you arent familiar with Thompson stroke motors its basically a hybrid power/economy build, typically they would use a roots and vane type supercharger that builds boost at low rpm easily, then hang the intake valve open upto 21 degrees into the upward compression stroke, thus reducing the amount of power needed to compress the intake charge by up to 30% while retaining volumetric efficiency at whatever atmospheric pressure you could get the motor to handle. I played with this long ago and far away with other peoples money, I still service some of those builds today.

So I've been thinking of taking those general principles of keeping the intake charge in the cylinder with boost while hanging intake valve open to reduce compression losses, thus yielding greater power, efficiency, and possibly lower emissions. As I love my D series I thought id start experiments on that platform, though K series makes more sense, I just don't like the bore/stroke and vsa/displacement ratios and feel they may need extra attention to internal geometry.

I'll be going at this in stages, stage 1 is nearly complete, just details to button up and mk2 will be logging data for me. I'll get baseline mpg and whp measurements, after some tuning of course, going to be a crash course in the finer nuances of smanager as I get her dialed in.

Stage 2 will be flex fuel conversion and tuning, I may also convert to COP ignition at this time with cdi planned upgrade for boost, on deck for that conversion is a 80 psi max 260lph e-85 compliant fuel pump, adjustable rising rate fpr and 510cc e-85 injectors. Some fuel line upgrades as well I think, I need the fuel pressure as low as 34 psi when running 91 octane, and it seems the regulators im looking at need a 5/16 line on return to flow enough with the pump i have chosen.

Stage 3 will add boost on the stock cam, probably a .45 trim ceramic ball bearing t3 with .48 ar housing and the second step turbine wheel (hard to find), the intercooler needs to be smaller or response is lost, so probably an audi a4 unit. At this point I'll log mpg and whp again, then I'll dial in the tune and do it again. No idea how e-85 tuning is going to work out so I need a baseline before the next stage so I can extrapolate.

Stage 4 should see gains in whp and mileage, ill have a cam ground where the intake valves in vtec hang open a certain amount of crank movement, they will close approximately 10° crank rotation before the instance of 90° which itself may need adjusted via offset wrist pins and main bearing bore alignment, once turbo starts to spool vtec lobe kicks in and Thompson strokes the motor, reducing the amount of power lost compressing the next cylinder to fire each time by up to 30%.

Stage 5 will be a custom geared trans built to capitalize on the specific power curve of the resulting Thompson stroke turbo engine. That's going to need a bigger brain than mine and I hope bense and tranzex feel free to chime in by that point.
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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Discussion Starter · #3 ·
The R may well fit too, but yuck to every chassis I could afford to build 🤢 the ratios however are near perfect, heat soak in the head from a turbo may cause driveability issues though. Im thinking go a step further than the traditional super charger, with the ability to alter cam timing or entire lobes it should be feasible to run a 9.4:1 or so until spool starts, then vtec lobe drops static compression to around 8.1:1 and getting the start of compression building to much closer to the instance of 90°, with pwm boost control dialed in to generate ideal dynamic compression ratio for conditions... its all just possibilities so far, thus the thinking about it. The R is a real possibility as the idea progresses.
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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Discussion Starter · #5 ·
It seems to me the exhaust side of the r head would have heat issues running a small turbo with higher than normal drive pressure. Could and may likely be my imagination , I havent ever really played with the r. I think I've put an intake on one and a cat back system on another, and one head job, so next to no experience with them.
 

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Discussion Starter · #7 ·
CA smog isint going to let me drop in an r18 without 6 months worth of paperwork, not having that paperwork done results in an impound fee and destruction of the car now. But there are carb legal routes for me to build a d into a Thompson stroke. I may buy a beater to test on the r with later, with the intention of ditching the chassis after everything is sorted and carb exemption is ready. More importantly I have much more experience and more sources for spare parts with the d platform, figuring out fueling and injector timing to make this work best will be enough on my plate without scrambling to learn a new platform I think.
 

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Discussion Starter · #9 ·
Thats actually a very good idea, COP ignition would be easy that way, and thats a roller valve train further reducing friction. I'll have to find an a2 head to cannibalize, I do have a y8 head sitting, though it needs a couple exhaust valves.
 

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Discussion Starter · #10 ·
I wonder if i could scrounge up a 3 step vtec head?🤨 Stroke it to 1.7, run a mostly stock single intake lobe, a mild Thompson stroke lobe on 2nd valve for low to medium boost (3-5 psi) and a further retarded higher duration vtec lobe for higher boost pressures. That would take care of all my d series bucket lists in one shot😃

A ported z6 oil pump should be able to operate that reliably as low as 1700rpm with my favorite 10w30 synthetic oil with 20% synthetic Lucas oil additive to bolster surface tension. The increased displacement would no doubt help low end torque and turbo spool, making Thompson stroke effects kick in that much sooner, and having a third option for high load situations would undoubtedly help in making it carb compliant. With a little elbow grease and a LOT of tuning I might turn this into something.

They are going to want some sort of carbon canister for blow off i bet😢
 

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Discussion Starter · #12 ·
Slight issues finding a 3 stage head, waiting on rods currently to start notching the block and girdle, searching for an appropriate turbo, intercooler, ect.
I do have my backup Z6 head apart, getting ready to port match a spare intake manifold in case I cant find a 3 stage head that isn't cracked. I also need to source an Hx 3.73 geared s40 trans.
Hondata ecu from xenocron should be here in the next couple weeks so I can start getting swapped over to flex fuel and dialed in.
 

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Discussion Starter · #15 ·
Dont worry about ignition timing too much, stock is fine, scaled for boost. Feel free to advance to your hearts content once on the dyno, and find your torque sweet spots lol. With high alcohol concentration, 80+%, and a reasonable/not too crazy max dynamic compression ratio target (no 14:1 static comp with 40lbs of boost haha), youll never really need to worry about detonation. On E with reasonable boost, most of the time you'll safely reach MEP, and safely overshoot it, before you ever see knock. E is sweet lol.

Still, have your det can listening while you creep up the timing if boost is high.

To get it running on E pretty well, add 20% to your base fuel table using the flex modifiers in SManager.

Then simply tune on the lambda scale using your wideband. Lambda 1.00 is always lambda 1.00, regardless of fuel type :)
Static compression will be roughly 9:1, dynamic will depend on what lobe its running and what load its at, so 1 valve mode would likely run until 5 psi, about a 12:1 dynamic, when the second valve opens and stays open til 20°ABDC the boost limit will be somewhere around 12 psi to reach a maximum of roughly 12.5:1 dynamic, on the high lobe with both valves hanging open until somewhere between 28 and 32°ABDC boost could go as high as 28psi before reaching 13.5:1. once I get the pistons, rods, crank done ill start degreeing in the cam profiles to see exactly when ivca needs to be to effectively destroke to 1.55L (2 valve) and 1.4L (high lobe).
 

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Discussion Starter · #18 ·
So with the 61 Ford f100/250 build ill have the capitol to finish the flex fuel conversion and probably add some form of CoP ignition, ive got crank, pistons, and block for the bottom end. some stuff I'd like input on, just to hash things out in my own mind; 137mm rods, or the b18 c3/5 rods? Darton MID sleeves or CSS? And is there some way to put the 3 stage on the z6 head? (Having trouble finding a 3 stage vtec head that isn't cracked or has a couple exhaust valve seats blown through)
 

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Discussion Starter · #20 ·
It was actually done much earlier, back in the 60s when superchargers first started appearing in cars, Ford even had a production version with a side mounted charger in some of the falcon police interceptors. I played with them back in high-school, and gains in torque and mpg were very nice, but back then turbos didn't seem like an option, and I was just beginning to play with vtec.
 

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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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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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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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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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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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