For those that have done the 3.5L conversion. What did you do as far as tuning? Wouldn't increasing the stroke also alter the timing?


Juker008

 

you dont have to tune anything.

 

So I have been told, but increasing stroke would upset the stock timing parameters. Wouldn't it?



Juker008

 

If you are that worried about the timing, use a piggy back chip so you can fine tune the engine.

 

Stroking it would also increase the compression ratio between 0-0.5 points not sure what it is exactly but its around there.

So in that sense tuning would be great especially if you have your car already tuned to run as lean as safety will allow on the 3.2 w/91 octane.

Mine already pings around 5K and im not even leaning it out at that point.

So I would just retune it.

 

timing is fine. ive been running it for over 6 months hard to redline many times, and the motor is very strong. if you are staying n/a, just get an air fuel controller.

keep in mind the guy above is running a stroker w/ an accord. meanwhile our type s ecus are geared towards a more aggressive setup. not to mention he only has access to 91 octane, while we can run 93.

 

I am not sure, but I am running .25 OB RL pistons in my 3.5L conversion n/a and am running lean. If I'm not mistaken the RL pistons cause greater compression so I may be the odd case compared to the others using stock CL pistons. Some of my plugs are burning out and I need to add a new fuel pump and pressure regulator.

 

i'm running standard RL pistons too, so my compression is the same as yours which should be 11:1. not sure if i'm leaning out tho, need to get on a dyno this month. p.s. i have a stock fuel pump and FPR if you need new ones. i'm using 255 walboro pump, and eventually hooking up an AEM FPR.

 

Thanks for the offer on the stock equipt, but I think I'm going after market stuff too. How is the walbro pump working for you? Looks like that's not an inline but more of a replacement for the stock?

 

exactly, replacing stock pump, i did all new filter and housing while i had the thing open. also just upgrade fpr and you can spray more fuel.

 

I'm not worried about the timing, I just want to know why it is that you can increase the stroke and not change the timing?

Now I haven't been on the boards for some time, ever since I got my M Coupe and turbo charged it. I wanted to know what are the fastest times that others have posted. In the past mine was 13.5 @ 106 w/ a 100 shot, then a 13.1 @ 108 on a progressive 150 shot. So what are the times of othes? If possible could you guys also state the power adders? BTW the MC does 12.789 @ 114.


Juker008

 

increasing stroke would change mechanical timing which is made up for with the cam gears etc...

ignition timing is a different issue and what needs to be looked at is the cam sensor and its pick up and ECU issues.

 

holy crap, haven't spoken to you in a long as time man! how've you been!

 

quick question....

anybody know what the EXACT size of the .25 OS RL pistons are in MM??

I am doing math now..but i suck.

thanks!

 

Your somewhat making sense, although I do need you to elaborate more. The way that I'm seeing it is that the CR will stay the same, but since the initial stroke is longer timing would be mechanically retarded.

Ehhh I'm all confused.



Juker008

 

OMG Sly, still listening to techno tracks. I've moved along. I still have the CLS, but I haven't driven it in more than a year, no exageration. FK I think that the tyres have already flat spotted . I've got my M Coupe, and I've turbocharged it. Nothing better than giving old model Vipers a run for their money .

All I'm doing now is parting out my CLS and getting ready to sell it. I figure that I'll get a 328, build it and make over 6, and trust me its easy .


Juker008

 

OMG Sly, still listening to techno tracks. I've moved along. I still have the CLS, but I haven't driven it in more than a year, no exageration. FK I think that the tyres have already flat spotted . I've got my M Coupe, and I've turbocharged it. Nothing better than giving old model Vipers a run for their money .

All I'm doing now is parting out my CLS and getting ready to sell it. I figure that I'll get a 328, build it and make over 6, and trust me its easy .

Oh something else that will make you guys . Remember Scalbert? Well he found one of my post on a BMW forum and hit me up. That SOB got himself an M Roadster. Oh and were did he find me? In the forced induction section. Leave it to Scalbert, man wants to turbocharge everything. I worry about his daughters' bigwheels.


Juker008

 

I may have confused you or me..

look at it this way..

the stroke is longer...but you divide it in maybe two parts...up/down..so lets say you have a jseries that is 89mm stroke and one that is 93mm...well the deck will be raised up only 2mm...because the overall difference is 4mm but upwards only 2. Therefore you can get away will....adding maybe one more tooth to a slightly longer belt....or purposely putting the timing marks on the cams differently so you dont bend valves...because the stroke will take longer...by a mere fraction of a second...

so all in all...yes perhaps retarded...slightly...but then again if the engine was design one way in the beginning or we change it properly...is it really retarded?

 

Uhhh, yea. Thats how I see it. So to say, that you are getting an additional 4mm of additional stroke, you are gaining more (power). So yea there should be an increase in power, without adjusting timing. That is only evident if the power gained is greater than the power lost do to retarding. See my confusion. There has to be a formula to be able to calculate that in advance; i.e. BSFC should be able to play a key role in determining,. in advance, if stroking without adjusting timing will net any additional gains.



Juker008

 

Wait, what?

Ignition timing is a function of crankshaft angle. How would a longer stroke change the degrees BTDC?

Ditto for mechanical timing.

 

Wouldn't a longer stroke equate to a longer combustion duration? At the same time I'm starting to see why you guys are refering to crankshaft angle. The revolution does not increase, i.e. more teeth on the crank. But where in relationship to the position is the piston at (hypothetically) 270 degrees; pre-stroke, vs 270 degrees after being stroked? If the piston is lower in the combustion chamber during the initial compression stroke, and spark fires then you are technically advancing timing, if it were the other way around then you are retarding timing. What I'm tring to get at is that I believe that with increased stroke you change the position of the piston, without tellign the ECU of the change.



Juker008

 

whats the problem?

typeR ran a 13.3 all motor. i have run 2 seperate M3s (e46), both were slightly modded, and i hung with them no problem past 100mph.

do you need more proof?

how are you going to advance timing? to my knowledge, the ONLY thing so far available to adjust timing is the emanage, and then that could only PULL timing and not advance it.

 

You're overthinking it. All of the additional displacement is at the bottom of the stroke. The spark fires at x degrees BTDC no matter what, and (given the same CR), that equates to the same distance between the pison crown and the head whether it is 3.2l or 3.5l.

Combustion "duration" is the same, pretty much. What does change is the piston speed, since it is travelling further per cycle.

 

Using the CLS pistons with my 3.5 along with the Walbro fuel pump here.

 

<<< Going to use CL-S pistons with my A1

 

IIRC doesn't Comptech sell a piggy back that allows the ability to adjust timing. I remmeber back when Scalbert was using it for his turbo project. Granted he was using it to retard timing, but then again, he is adjusting timing.

If you hanged with E46s I would assume that you are running at least a 13.5, this number given by the worst E46 driver out there . On average the E46 drivers/owners that I know cut 13 flats consistantly. Lets just say that you are doing 13.5. Taking my 5AT CLS that was doing 14.7 w/ CAI & headers, it took an additional 100 wet shot to get to a 13.5 . IIRC doesn't a 3.5L conversion give roughly 45 extra ft/lbs . Where's the other 55, SCer?



Juker008

 

To me this is sounding contradicting. If the same distance between the piston crown and the head is the same, then where is the increased diplacement (storke).

This is the insight that I'm seeing; piston speed is increased. Then again, if piston speed is increased, while flame travel speed remains constant, and TDC dwell has been decreased due to increased piston speed, then theoretically timing has been retarded.

Man, I've been staring at my monitor for over an hour writing this single post. If you were to imagine my thoughts right now, they look like a ball of twine.

I'm going to go ahead and contact Scalbert on this issue, perhaps he can untangle my thoughts. Although I would, and greatly appreciate all the info/input that you guys are feeding me.


Juker008

 

I am not an engineer, and I've never rebuilt anything bigger than a v-twin, so I could be wrong, but this is how I visualize it.

Moving the big end of the rod further out from the crank centerline increases the stroke. Moving the wrist pin higher up on the piston (or shortening the rod) keeps it from crashing into the head, so the net is additional displacement at the bottom of the stroke.

As for dwell, well maybe... But I think it is offset by the increased rod angle at TDC. The piston is moving faster, but the reversal at TDC takes approximately the same time, because the arc that the big end is tracing has a larger radius than before.

 

I see what you are both getting at...

Basically your main concern in my head is the ECU knowing when to fire sparkplug...IE:ignition timing..

HOWEVER do to cam sensor etc...and proper mechanical timing...the ECU would know when to fire the plug anyways..

right? Now i am getting confused..

PS_and firing of injectors.............

 

my mods off the top of my head, i'm sure i'm forgetting a few things...

block was stripped down and acid dipped, cylinders rehoned, 3.5L crankshaft mild polish, 3.5 rods w/ RL pistons for 11:1 compression, every nut, bolt, and gasket was replaced. assembly balanced with underdrive unorthodox lightweight pulley. heads were cleaned up. lower intake runner hand ported, upper intake manifold extrude honed. thermoblok spacers, underdrive pulley kit, bored throttle body, VSA throttle body delete, comptech icebox, comptech headers w/ jet hot, random tech hi-flow cat, full 2.5" catback w/ borla resonator/mufflers/tips, walboro 255 fuel pump, mugen thermostat/fan switch

again, to the best of my knowledge, people were only able to pull timing and not advance it, not sure what equipment they were using other than emanage.

 

3.5L Conversion, balance, underdrive pullies (including crank), intake, headers, exhaust, .6 RC increase, PnP head, bored TB, all this gave you an additional 100 to the wheels? If so, wow. So what are your times and traps with all this? Mostly curious about your traps.



Juker008

 

not sure but im going to dyno soon, its not always about hp, torque band is the main gain in the stroker