Engine is bucking while cruising

[gruff511]

I recently installed new cams and now im getting a bad bucking issue anywhere lower then 2000rpm while cruising. Its so bad the car wants to shake itself apart. Usually only under light load and foot just resting on the throttle. Ive read in other threads to turn off AE and fuel cut so i did all that and still same issue. The only thing i noticed that reduces the bucking to not be so violent is to run really low ignition timing and i dont like that because my Exhaust Temps get really hot while just cruising and heatsoaks the motor and feels really sluggish and has no power. Even if my AFR's are rich or lean it will still do this.
Im not used to larger then stock cams so im not sure if i should be running more or less timing then when i had stock cams. Ive read i need to run it a little richer but running rich doesnt help. And ive never had this bucking issue before in the past with the stock cams, i only started to experience it once i put the bigger cams in. Its a real PITA right now because there is no light load cruising below 2000rpm.
i included my latest msq and a piece of a datalog, i wasnt able to upload the whole log it says its too large.
And the setup im running is an MS3X on a eclipse 2.0l 420a with 8.8:1 compression and stage2 cams.

[billr]

I gotta ask... what rpm range does the cam manufacturer claim those are intended for, what is the description of idle quality to be expected?

Edit: Never-mind, I see in your other thread that these are crower 64462-2, 2000-7700 rpm, "definite lope at idle". What is still undefined, though, is what they consider Idle speed to be...

[gruff511]

I gotta ask... what rpm range does the cam manufacturer claim those are intended for, what is the description of idle quality to be expected?

Edit: Never-mind, I see in your other thread that these are crower 64462-2, 2000-7700 rpm, "definite lope at idle". What is still undefined, though, is what they consider Idle speed to be...

Other guys I have talked to that run these cams and even the stage3 cams say theirs idles nice between 800-900rpm but thats on a stock ecu.

[gruff511]

What i noticed is that when im in 1st and 2nd gear it doesnt do the bucking and shaking, but when in 3rd gear i start to feel it then in 4th gear you really feel it, and 5th gear the car wants to shake it self apart. And this is only below 2000rpm anything above 2k rpm it runs normal

[dontz125]

This sounds like an EFI version of the old Burns and Allen sketch; "Tuner, tuner! My car shakes badly when I drive below 2k and above second gear." "So don't drive like that!"

Downshift! You're not 'carbureting' properly, you're barely charging your battery, and the oil films on your bearing surfaces probably don't appreciate the impact loading ...

[turbo conversion]

I agree with dontz125, with lumpy cams you need to keep the rpm in the area where the engine smooths out for crusing.

That is the down side of large cams with a manual transmission, you loose stock drive ability , automatics dampen this through the torque converter.

You really need to put more timing back in the lower rpm range, like you said the cylinder temps are going to high not good.

I would set idle to what ever makes the engine happy (lowest most stable map), don't get to hung up on rpm numbers every set up is different.

David

edit: text

[gruff511]

Thanks guys, i agree with everything you say. Im just asking about the bucking because ive seen people with the same issue then they fixed it so i wasnt sure if i just have some settings wrong.
i dont mind it idling high or driving in the higher rpm i just wasnt sure if these issues are normal.
These cams arent an aggressive cam but i dont know much about larger cams i just hear on the 420a forums their cars run the same with these cams on stock ecu, so i was thinking my tune is off somewhere.

[gruff511]

Only other question i have is, do larger cams usually need more or less timing while cruising? Or do i just need to adjust timing to where it feels good?

[turbo conversion]

Only other question i have is, do larger cams usually need more or less timing while cruising? Or do i just need to adjust timing to where it feels good?

Tune fuel and timing where the engine is the smoothest.

What are the actual specs on the cams?

David

[Nbgorman]

Hey, Im running a 420a with crower stage 2's and 10:1 compression, my base timing is around 13° and about 10 after calculations auch as idle advance and load advance are calculated. For a while I had it idling smoothly at around 750 Rpms, but my vaccuum wasnt as high as I wanted it, so I bumped it up to 965 once operating temp was achieved. It sounds to me like you have to degree your cams. I had a similar issue when I first started tuning. If you would like, I can put my tune up for you to try out

[gruff511]

http://www.crower.com/mitsubishi-420a-e ... -6179.html

These are the cams on the crower website, it gives full specs at the bottom

[turbo conversion]

http://www.crower.com/mitsubishi-420a-e ... -6179.html

These are the cams on the crower website, it gives full specs at the bottom

Have you done any of the mods Crower require on the spec. sheet?

These cams are fairly radical and will probably idle about 1000-1100 rpm.

You will need to go with a lower differential gear ratio than stock to get full benefit of these cams along with other mods,
that will also help with your drive ability issues.

When you change cam profiles you need to change everything else to make it all match.

It tells you on the spec sheet what is required and recommended, with out these mods it will never run as it should, been there done that

David

[gruff511]

http://www.crower.com/mitsubishi-420a-e ... -6179.html

These are the cams on the crower website, it gives full specs at the bottom

Have you done any of the mods Crower require on the spec. sheet?

These cams are fairly radical and will probably idle about 1000-1100 rpm.

You will need to go with a lower differential gear ratio than stock to get full benefit of these cams along with other mods,
that will also help with your drive ability issues.

When you change cam profiles you need to change everything else to make it all match.

It tells you on the spec sheet what is required and recommended, with out these mods it will never run as it should, been there done that

David

Well ive been in other peoples cars that run these same cams and stage 3 cams in the same exact motor and a couple were running megasquirt and another one a stock ecu. Theyres ran perfectly fine, they idle at 900-1000rpm good and drive smooth while cruising between 1000-2000rpm.
Which is what makes me think its in the Tune.

[gruff511]

Hey, Im running a 420a with crower stage 2's and 10:1 compression, my base timing is around 13° and about 10 after calculations auch as idle advance and load advance are calculated. For a while I had it idling smoothly at around 750 Rpms, but my vaccuum wasnt as high as I wanted it, so I bumped it up to 965 once operating temp was achieved. It sounds to me like you have to degree your cams. I had a similar issue when I first started tuning. If you would like, I can put my tune up for you to try out

Yes would you post your msq. So i can take a look at it? And did you end up changing the degree of your cams?

[turbo conversion]

http://www.crower.com/mitsubishi-420a-e ... -6179.html

These are the cams on the crower website, it gives full specs at the bottom

Have you done any of the mods Crower require on the spec. sheet?

These cams are fairly radical and will probably idle about 1000-1100 rpm.

You will need to go with a lower differential gear ratio than stock to get full benefit of these cams along with other mods,
that will also help with your drive ability issues.

When you change cam profiles you need to change everything else to make it all match.

It tells you on the spec sheet what is required and recommended, with out these mods it will never run as it should, been there done that

David

Well ive been in other peoples cars that run these same cams and stage 3 cams in the same exact motor and a couple were running megasquirt and another one a stock ecu. Theyres ran perfectly fine, they idle at 900-1000rpm good and drive smooth while cruising between 1000-2000rpm.
Which is what makes me think its in the Tune.

Then all you have to do is get an msq from one of these people load it and your problem should be solved.

David

[gruff511]

I did get an msq. from a friend who has the stage 3 cams and tried it out and i still have the same problem. He is also still using the factory cam gears so he did not degree in his cams and it runs great. Im thinking i may need to get some adjustable cam gears to adjust the cams but i want to make sure thats my problems first.

[billr]

"He is also still using the factory cam gears so he did not degree in his cams and it runs great. Im thinking i may need to get some adjustable cam gears to adjust the cams but i want to make sure thats my problems first."

That makes no sense. If he is using stock valve timing successfully with that cam, why do you think you must alter the timing? Is everything identical on the two engines (not just cams)?

[gruff511]

Well he is using the stge 3 cams and i have the stage 2 and i dont know the specs of the stage 3s but i heard it depends on the amount of overlaps on the cams. When i get off work today i was going to do some research and compare the cam profiles and see if they are much different

[billr]

Okay, I missed that... you have different cams. Wait for somebody with the same cams, injectors, etc. to share an MSQ.

[kaeman]

On the vehicles that have performance cams in them that are running with no bucking, what changes have been made to the vehicle, have the tires and rims been changed to shorter tires, etc. Just because they haven't changed the gearing in the trans, they may have changed gearing using tire height. If your cams are bucking under load and light throttle, another thing to check is mechanical causes of bucking, I have an old 4 speed el camino and when I was idling in gear or doing low speed cruising in high gears, the vehicle used to buck... I found a bad motor mount and a loose pinion. tightened the pinion and replaced the motor mount bucking gone. don't discount possible bad mounts or cv joints etc.