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stroker kit question.(tuning)

Swift

Swift

Experienced Member
Joined
2 June 2006
Messages
769
I figured I would ask a technical question here since we have alot of very experience people here in regards to increasing stroke. My question is simple and yet I cannot think clearly to find the answer. The question is this: If you increase the stroke, lets say a 3.8L stroker kit, would the ignition timing need to be advanced or retarded based on the time it now takes to reach TDC? Longer stroke would equal slower piston speed but thats all I got.

thanks in advance.
Ben

Ps-If thread needs to be moved feel free.sry
 
FWIW, here's a graph of the comparable piston speeds:

SoS_piston_acceleration.jpg


And reciprocating force vs. RPM
SoS_reciprocating_force.jpg


Shad at Driving Ambition or Chris at ScienceofSpeed would be great resources in answering your questions.
 
The ignition map changes completely between a standard engine and a stroked engine due to the incredible differences in engine performance. So, there's no universal response to your question. The peak ignition angle depends more on things like compression ratio and whether the engine is NA or FI. Maybe if you ask a more specific question, someone can help.

Cheers,
-- Chris
 
Good question: what is the maximum difference in degrees between the stock ignition timing on an OEM US 3.0 and the timing actually programmed into the engine computers of naturally-aspirated 3.8 liter engines that have been built to run on pump gas. The timing of the individual 3.8s will likely vary based on the intake, exhaust, cams, etc. used, but there should be some real data out there. Is the shift from OEM constant, say +3 degrees across the board, or does it vary? Hopefully this is not too specific and hopefully the data is not confidential!

Hmmm, maybe the FI forum is not the best place to discuss NA engines, though.

Anyway, regarding the piston speed and time it takes to get to TDC: at any given RPM, the piston will complete one stroke in the same amount of time, regardless how long that stroke is. At 60 RPM, the piston will go up and down once per second. The longer the stroke is, the further it will go up and down in that second. Therefore longer stroke equals higher piston speed at any given RPM.
 
the bigger question should be- is the rod angle changed/increased with the new crank?
 
swerve said:
the bigger question should be- is the rod angle changed/increased with the new crank?
Click to expand...

ICBW and maybe Chris can chime in but I'm pretty sure the rod angle are as follows:

OEM crankshaft: 14.9 degrees
Stroker w/ 88mm crankshaft: 16.8 degrees

Sidewall loading of the stroker is just incrementally higher than stock.

Chris, where you at, foo?
 
The the reality is that the piston speed and geometry changes will have less affect on total timing than the other changes you would almost certainly make to the motor during that build, such as changing compression. Also, when you tune the stroker motor, you are using a fully programmable ECU and trying to get the best performance you can without dangerous cylinder pressures. The stock ECU has a much, much wider margin of error, as manufacturers do not want to be replacing motors every time some owner has a brain fart and puts lower octane gas in it. I can't imagine it not having a more aggressive timing map than the stock system.

If you are really just asking about tuning theory and the effect of geometry changes on tuning in general, you might jump over to the NA forum on Honda-Tech; there are a couple of great builders there and many good tuners. I have picked up some good info on geometry changes there.
 
Ponyboy said:
Sidewall loading of the stroker is just incrementally higher than stock.
Click to expand...

If I'm not mistaken, the sidewall loading is 13.9% higher than stock.

My personal interest in the question isn't about tuning theory, but in the actual degrees of difference in the timing. At least the early NSXs allow you to advance or retard the timing (page 23-91 of the '91 Service Manual). Maybe this is enough to get the timing relatively close to optimal for a 3.8 liter while retaining all the fail-safe systems built into the OEM engine management. Without knowing the actual degrees of difference between OEM and a dyno-tuned SoS 3.8, it's all just guesses and heresay, though.

If anyone has experience with this, I'd love to know what the actual figures are. To quote Ponyboy: "Chris, where you at, foo?"
 
WOW! thanks guys for the help so far and yes the theory etc with it. Now i will get more technical.

I will make comparisons for you in regards to the 3.8 stroker compared to my built engine.

Now if some of you dont know i have a built stroker 3.5L in an Acura Legend. Now the theories are the same and there are some similiarities, like i can use the timing adjustments screw to advance or retard 5 degrees.

Now the finer points are that I did increase compression ratio from 9.6:1 to 10.5:1. The fuel rail pressure is also higher by about 10psi. I am running 3.2 cams that are built for higher end RPM not torque so slightly less lift but more duration however i did not swap springs and they are not as stiff.

The reason I had to come here and ask is because I have ran about 3 ECUs and a chip. The first ECU is for a less agressive duration cam and the mapping coupled with my fuel pressure SHOULD result in me running rich and timing retarded overall. I also used my original ECU with a chip made for this setup and it did if fact seem to run rich and the timing was advanced. Now the fun part. This ECU had damaged done i believe because of the socketing process and does not work. I then installed an AUTO ECU which works with a STOCK chip that would be made for the cams i have installed. The car runs GREAT! However I keep coming across the problem that around 5k rpms the power starts dropping and the engine tone changes to make me think I may be detonating. In all my testing i did a few months ago I came to the conclusion I am not getting enough fuel volume top end because i have a custom intake with shorter intake runners (2 in VS 6in) to have better topend suited for the cams.

So now I will put in terms you guys will understand and hopefully Shad or some others will have a good answer.

***Take your 3.0L and create a stroker kit by swapping crank/rods/pistons. BUT leave your STOCK heads on and perhaps put in a slightly longer duration cam but dont change your valve springs. Now you are still running your STOCK ECU and electronics and have increased fuel pressure on stock injectors. You have not upgraded fuel pump though.

So now what SHOULD be done to fine tune this into a more perfectly running machine? Thanks for all the input so far and I love theory and love learning as much as I can. As for testing it SEEMS that if I advance it with the timing adjustment screw around 4 degrees it actually seems worse at 5k plus?

thanks again,
Ben

Ps-The engine is NA at the moment but will be getting supercharged come spring i hope.(6-9PSI)
 
simple answer=sell your ecu's, buy a aem ems unit and take it to a repuatable tuner in your area, honda-tech would be a good place to ask about a great tuner in your area
 
"SHOULD" will always land you in hot water. tuning is never "should" it "IS".

you can find out best ignition timing on a load bearing dyno. it completely takes the guess work out of ignition advance tuning. tuning is not an art. its a science.

there is no such thing as if your running x psi of boost, you need to pull x degress of timing. thats guess work, not tuning. anyone that "tunes" according to guess work should not be tuning cars.

i recommend dyno dynamics since thats the setup I have and also used in efi university.

With a stroker, its time to go stand alone. Personal perference is AEM since its easy to tune and there are no "special" software issues like the HKS Fcon Vpro. :rolleyes: where only retailers are given software.

personally, i can do a better job than the tune in my car, but due to the inability to get the Power Writer sofware, i need to get AEM. :rolleyes: talk about stupid business practice. personally i will never recommend HKS ecu to any customers since it limits their option of tuners... which i guess to some is a good thing :rolleyes: running AEM on two of my other cars and going to get it for the nsx.

anyways.

on the dyno dynamics dyno, use the real time sampling screen. set a base ignition timing. Lock the car down at the desired RPM. advance timing till real time sampling HP levels off. your at MinBT as opposed to MaxBT. MinBT has a built in margen of safety. No guess work, just using what the dyno and the car is telling you.

Fuel first, then ignition timing of course. I use boost comp, make sure to setup the iat compensation table.

For low boost such as 1-15 psi (depending on car ofcourse), you can run the car under load. stop then let the car return to normal operating temp. for higher boost 20-30psi, you'll need to do sweaper runs to find bet ignition timing and fuel since heat generated by the engine when sitting still will cause increase coolant temps, detonation and other fun effects.

after the car is dialed in, clean up and perfect the tune for highway cruse and mpg.

get the car into the hands of a good tuner. I recommend someone with a load bearing dyno. The inerta dynos leave a lot of tuning to guess work and is no longer the industry standard. I seen blown engines all the time from a dynojet tune. got a shop next door that has an inhouse tuner thats blown up his fare share of motors... including his own, this 2 buddies and lol, who knows how many other ones i dont find out about. :tongue: looks great on the dyno, 5 minutes of street "tuning" and its ready to leave the shop. then it blows when the customer is driving on the highway :biggrin:

lol then they tell the customer, oh one of your injectors was 10% under or your motor was getting old... or you must have gotten a bad tank of gas.:rolleyes:

i see them rebuilding a lot of motors that they tuned, at least 1 -2 a month. :biggrin:

guess who gets stuck with the bill for the motor rebuild. *sigh*

Happy motoring.

Rob
 
Last edited:
RON98 said:
With a stroker, its time to go stand alone.
Click to expand...

We're getting off topic, but why is it time to go stand-alone? According to the 1991 Service Manual, the stock ECU contains maps for:
  • ignition timing
  • injector timing and duration
both of which are based on manifold pressure and engine speed.

The ignition timing actually sent to the igniters is based on the map but may be modified depending on inputs from the knock sensors and the coolant temperature sensor. The injector timing seems to be determined only by the map. The injector duration is based on the map but is also influenced by inputs from the intake air temp sensor, oxygen sensors, traction control sensor, etc.

If a stroker needs different ignition and fuel maps, these could be programmed into a new chip. Is it time to go stand-alone because:
  • the ignition timing can only be adjusted within a limited number of degrees
  • the fuel pulse cannot be made wide enough to supply enough fuel using the stock fuel pump and injectors and if an uprated pump and injectors are used the additional inputs from, for example, the oxygen sensor signal screws it up
  • the ignition timing map can't be adjusted
  • something else?
 
My experience is if you change engine internals like more displacement, cams, high comp pistons, supercharger, turbo etc you always have to use a standalone. It is better for the engine and you get way more power out of the whole setup.
 
austrian type-R said:
My experience is if you change engine internals like more displacement, cams, high comp pistons, supercharger, turbo etc you always have to use a standalone. It is better for the engine and you get way more power out of the whole setup.
Click to expand...

i feel the same way.

personally when it comes to control. i as a turner want control of 100% of the verables. I dont want the customer coming back asking a question about the tune... and my response be....

"well, its unperdictable with a piggy back systems since the factory ecu still corrects fuel based on stock o2 sensor feedback" etc.

i want to give them a straight answer.

fuel map and ignition map is all dialed in by hand. idle, iat, coolant compensation, knock sensor ignition retard, rev limit ignition retard & fuel cut, o2 sensor target and feedback are all personally input by me.

also intergrated boost, meth, nitrous, 2 setup, traction control is nice if the customer wants to use those options.

ask the tuner what system they run in their car. :wink:

the real questions should be why someone should NOT going to standalone. If the answer is money... then you should not be getting stroker/built motor since priorities are wrong.
 
The question to put in motor terms would be if all you DID was a stroker. So no head work, cams, or larger injectors.

So lets say you did a stroker kit on the 3.0 and also used a high compression piston(11:1) COULD it run effeciently off a stock ECU with a new ROM chip if more fuel was added and the internal timing was change...

Also the initial question is how much the ignition timing would have to be change if any.

Thanks for all the knowledgable replies..and yes I will be going AEM in about a year and FI.

PS- I think this is a good question for anybody thinking of doing anything performance wise to any car at what point a standalone becomes a part of the build.
 
ok. BASICALY with just a longer crank, slightly higher comp pistons you can run and drive your car, thats it simple and black and white.


however, if you plan on doing more driving than"brake in" style driving on your motor with the stock ecu that is when you want to have your engine tuned, you want to have everything run smooth, not too rich, not too lean, and you will find power you never knew you had with a oem ecu:biggrin:


if nothing else, just think of it as insurance for your motor, your about to put a stroker motor in a nsx and you are not going to tune it?


the only thing worse than blowing up a motor is blowing up a brand new motor you spend 10k on:eek:
 
Swift said:
The question to put in motor terms would be if all you DID was a stroker. So no head work, cams, or larger injectors.

So lets say you did a stroker kit on the 3.0 and also used a high compression piston(11:1) COULD it run effeciently off a stock ECU with a new ROM chip if more fuel was added and the internal timing was change...

Also the initial question is how much the ignition timing would have to be change if any.
Click to expand...

why get standalone in 1 year when you should be getting it now? i would not drive my car with a knot inmy throat for a year.

yes ignition defintily will have to change by now much, no one can answer with out guessing.

ignition timing depends on many factors, octane, compresson, piston speed, air density, piston design, head design, quench zones.

i dont think your getting the concept here. to do such a extensive upgrade, you have excelled beyond the FACTORY setup for the factory motor.

A rom tune is just fine, as long as it not a guess tune.

you asked for profeshional advice, your getting it. to put it to good use or not, thats up to you.
 
Swift said:
PS- I think this is a good question for anybody thinking of doing anything performance wise to any car at what point a standalone becomes a part of the build.
Click to expand...

I also think it's a very good question, even if it is a little bit off the original topic.

Why stock EMS with a reprogrammed chip when running a N/A engine?
  • Gut feeling number 1: for safety and reliability, in order to keep the OEM fail-safe systems in place. I'd think there's a lower chance of engine failure if not everything is reprogrammed, just the fuel and ignition base maps. I assume Honda spent thousands of hours programming not only the fuel and ignition maps, but all the other things in there as well. This is only one data point, but my car has had wilder camshafts, ported and polished cylinder heads, an increased compression ratio, etc. for the past 13 years. Right after the engine was modified, I had a chip programmed with the car on a dyno. I've driven the car like this for about 100,000 miles without any problems. The engine still pushes the car to 189 mph and at the last service, after I asked for a leak-down test, the shop said the engine still seems to be within OEM spec for a new engine. It seems to be pretty bulletproof.
  • Gut feeling number 2: So that the traction control, cruise control, and other ancillary features still work as the factory intended.
Why standalone?
  • If the amount of fuel that should be injected cannot be determined by just measuring the manifold pressure and the intake air temperature (as is the case with nitrous oxide)
  • If the intake air temperature goes so high that the stock computer doesn't know how to deal with it (I guess this could happen with forced induction)
  • If the manifold pressure goes above atmospheric so that the computer doesn't know how to deal with it (again, I guess this could happen with forced induction)
  • etc.
With nitrous or forced induction, I can understand why a stand-alone engine management system can offer more safety than a stock EMS with a reprogrammed chip. But with just natural aspiration, the manifold pressure won't go any higher than stock, the intake air temperatures won't go any higher, and you're always burning fuel in the same mixture of gasses. The same data inputs should suffice to determine the optimal amount of fuel to inject and when to ignite it. You just need more fuel and probably more aggressive timing, both of which can be programmed into a new chip in the stock EMS. If the EMS then tweaks the reprogrammed fuel curve because the oxygen sensors report that the fuel/air ratio isn't exactly where Honda said it should be, I'd think that should probably be fine. You need more fuel, but the fuel/air ratio Honda is shooting for is probably a good one.

I have the feeling I'm still not getting something here... On a naturally-aspirated engine, can you make more horsepower with a stand-alone EMS programmed on a dyno than you could with a chip for the stock EMS if that chip was also programmed with your car on a dyno? If the stand-alone can make more horsepower on a naturally-aspirated car, why?
 
greenberet said:
I also think it's a very good question, even if it is a little bit off the original topic.

Why stock EMS with a reprogrammed chip when running a N/A engine?
  • Gut feeling number 1: for safety and reliability, in order to keep the OEM fail-safe systems in place. I'd think there's a lower chance of engine failure if not everything is reprogrammed, just the fuel and ignition base maps. I assume Honda spent thousands of hours programming not only the fuel and ignition maps, but all the other things in there as well. This is only one data point, but my car has had wilder camshafts, ported and polished cylinder heads, an increased compression ratio, etc. for the past 13 years. Right after the engine was modified, I had a chip programmed with the car on a dyno. I've driven the car like this for about 100,000 miles without any problems. The engine still pushes the car to 189 mph and at the last service, after I asked for a leak-down test, the shop said the engine still seems to be within OEM spec for a new engine. It seems to be pretty bulletproof.
  • Gut feeling number 2: So that the traction control, cruise control, and other ancillary features still work as the factory intended.
Why standalone?
  • If the amount of fuel that should be injected cannot be determined by just measuring the manifold pressure and the intake air temperature (as is the case with nitrous oxide)
  • If the intake air temperature goes so high that the stock computer doesn't know how to deal with it (I guess this could happen with forced induction)
  • If the manifold pressure goes above atmospheric so that the computer doesn't know how to deal with it (again, I guess this could happen with forced induction)
  • etc.
With nitrous or forced induction, I can understand why a stand-alone engine management system can offer more safety than a stock EMS with a reprogrammed chip. But with just natural aspiration, the manifold pressure won't go any higher than stock, the intake air temperatures won't go any higher, and you're always burning fuel in the same mixture of gasses. The same data inputs should suffice to determine the optimal amount of fuel to inject and when to ignite it. You just need more fuel and probably more aggressive timing, both of which can be programmed into a new chip in the stock EMS. If the EMS then tweaks the reprogrammed fuel curve because the oxygen sensors report that the fuel/air ratio isn't exactly where Honda said it should be, I'd think that should probably be fine. You need more fuel, but the fuel/air ratio Honda is shooting for is probably a good one.

I have the feeling I'm still not getting something here... On a naturally-aspirated engine, can you make more horsepower with a stand-alone EMS programmed on a dyno than you could with a chip for the stock EMS if that chip was also programmed with your car on a dyno? If the stand-alone can make more horsepower on a naturally-aspirated car, why?
Click to expand...

you have a lot of I FEEL, IT SHOULD, IFs in your statement above. Im not a fan of leaving my motor's life up to feeling, should, could, maybe, think, gut feeling etc.

With AEM EMS, you dont lose any of "OEM fail-safe systems in place".

The only thing you dont get is traction and cruse control. I personally drive wth TC off anyways.

Stroker is different than wild cams. 3.8L displacement is significally different than 3.0 or 3.2L even if its a the same compression which it is not.

Also with quench zones changed by HG you cant if, maybe, should, could, the tune. Its just silly.

3.8L is a lot more air. more air/more displacement requires more timing for the flame front to travel through the cylinder. Also higher compression, the flame front travels faster, it also depends on piston dome design and a crap load of other factors.

hey im sure the setup on your car works great. but your WILD cams and this stroker are as different as apples and elephants.

Sure, if you get the car rom tuned on a dyno the car will be fine provided you can adjust both timing and fuel advance and retard.

In his statement however, he clearly stated that he is going FI.

On the currently setup alone, i would recommend standalone. Once again, your two cars are do different, what works for you probably wont work for him. If he has any problems based on your recommendation, will you send him a check for labor and a new motor? I tuned on a regular basis. Im sure your are very expereinced also, you must see the difference in the two motors. if his is going fi in the future, there is no reason why he would not or should not go standalone right now other than the costs.

im not a big fan of guessing. thats why i use aem and a load bearing dyno to tune based on facts. tuning is not a black art.

happy motoring

Rob
 
RON98 said:
Sure, if you get the car rom tuned on a dyno the car will be fine provided you can adjust both timing and fuel advance and retard.

In his statement however, he clearly stated that he is going FI.
Click to expand...

I read all of Swift's posts in this thread twice just now and I think :biggrin: he never said he is going FI. [Edit: He did day so at the bottom of post #11 and towards the bottom of post #17. Doh - I missed that twice!] He asked about ignition timing if you increase the stroke.

I agree that tuning should be done on a dyno and not based on guesses. That's why I spent the money to have my chip custom programmed on a dyno. However, I find this forum a great place to learn. So in order to learn:
  • as far as I understand it, the stock chip in an NSX ECU controls ignition timing, fuel timing, and fuel volume and these base maps can be modified if you put in a different chip. Is this correct?
  • in an NSX with FI or nitrous, more parameters should to be monitored and adjusted for than the stock ECU is designed for, so going to a standalone will provide more safety and/or horsepower, if programmed properly. Is this correct?
  • for a naturally aspirated NSX, be it a puny 3.0 (like mine) or a monster 3.8, the stock EMS monitors all the parameters that are required so a chip can be programmed while the car is on a dyno that will properly optimize the fuel and ignition maps (unless the engine needs more fuel than the stock pump and injectors can flow). Is this correct?
If someone knows these things and is not just making guesses based on their hunches (like me) I'd love to learn the facts. To be honest, I'd love to hear other people's hunches as well. Even if they preface their hunches with "I think" instead of presenting them as facts.
 
Last edited:
thanks for all the replies and good advice from both sides. I am asking this question for two reasons...

1) for anybody doing a stroker in an NSX
2) because of my motor and its relevance.

You see I do not own an NSX yet but i have attended a meet and one day will of course(why i am here). However I am in a league ALL MY OWN. If you see my sig and go to my cardomain I am in uncharted water with no experts to help me. I felt the members here knew enough to assist me without guess work. The NSX ECU and LEGEND ECU are very similiar and quite different then other honda ECUs. I had a ROM chip made based off a very similiar motor, only difference was compression...I was detonating BAD because of to much timing. So I am trying to figure out if he tried to toast my motor, made a mistake, or just because of an 11:1 compression VS a 9.6:1 that I was detonating. We have the same fuel supply also and stroke.

Anyways the car is sitting and i am running a better suited STOCK chip now however i still feel timing or fuel is off above 5k. The nearest dyno is 2hrs away and what they are worth i do not know. So I figured I would simply state a question to help me out.

I am a mechanic and built this all on my own. I PLAN on going FI soon running similiar to a CTSC style setup(6-9PSI) so then I will go AEM(1yr)

Thanks so far!
 

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