Car previously ran on BC3+ and car runs from idle to 8200rpm perfectly with only a slight bog in vtec transition.

Now just tried to do some testing with BC4. With the motor on the car we remove the BC3+ cams, locked the vtec rocker manually, put the BC4 cams in with the timing belt. Then we tried to dial the cams in with vtec lock to factroy center lobe of In102 and EX104. Then we had to remove the timing belts and cams so we can unlock vtec and then installed back the BC4 cams and timing belt.

Just tested the car just now. The car idles ok. At WOT, low revs almost like BC3+, then when it hit about 5400rpm vtec transition, the cars bogs badly and start like mis-firing till 6200rpm when it just suddenly goes and pulls really hard till 8500rpm.

after degreeing the cams, the cam gear was In +1 Ex + with the lobe center at In102 and Ex104. No additional tune was done on the car.

I did not want to send the car to dyno due to this reason. I want try to figure out why it bog so badly and mis-fires at vtec transition then only send to dyno.

Please help.. What could i have done or miss out?


motor info:-
JDM B18C5 stock bottem end
B16A ported head
ITR intake + TB
JDM DC 4-1

 

And also does anyone knows the lobe center of the primary of the BC4.

It was a real pain to lock vtec, dial in, then remove cams to unlock vtec, then install back everything.

So if anyone had the specs for primary of the BC4 will be good so i can try to degree them again.

 

My guess would be that your Vtec crossover point is set to low. From my experience, if you get a bog or power dip right after Vtec engagement, it's because it's set to low for those cams. I'm thinking it should be set somewhere around 6000 rpm but you really need to get it properly tuned. Different cams will require altered fuel and ignition maps to perform properly. If you're going to take the time to degree your cams, why not take the time to tune it too? What kind of engine management are you using?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 00Red_SiR &raquo;</TD></TR><TR><TD CLASS="quote">My guess would be that your Vtec crossover point is set to low. From my experience, if you get a bog or power dip right after Vtec engagement, it's because it's set to low for those cams. I'm thinking it should be set somewhere around 6000 rpm but you really need to get it properly tuned. Different cams will require altered fuel and ignition maps to perform properly. If you're going to take the time to degree your cams, why not take the time to tune it too? What kind of engine management are you using?</TD></TR></TABLE>

I'm just trying it out on my old setup with just a J's Racing N1 endurance ecu which ran really well with the BC3+ to make 184whp with a rich a/f of about 11.5-11.8:1 at peak rev.

I just want to try to make references with everything else same but with just a cam change to BC4 and setting the cam up to run properly with this ECU as i believe will provide sufficient fuel as it was rich with BC3+.

I have a Hondata S300j but thought i want to try mechanically playing around with the cam timing to make them work properly then do a dyno with just a change of the BC4 to compare with the previous BC3+. Then bolt on my Hondata S300 and get it tuned to see how much more i can get from a dyno-tune.

All this just as references for myself which i will eventually post it up here for everyone.

 

Anyone with any experience of these BC4 who can me their lobe center line that made good power on their motor?

Anyone with the primary lobe center on these BC4?

DonF , Tbone , B19coupe , Guilotine , Chillnit , Ausmith ??? Anyone??

 

The absolute best way to determine the gains from one part over another is to have the engine tuned perfectly with the old setup first. Change 1 part only (cams in your case) and then completely re-tune the car so it's at optimal performance again. Whatever the difference in power, is a true "apples to apples" comparison.

By not retuning with the new cams installed you're comparing tuned parts to untuned different parts....hardly fair.

Also the more radical the parts are that you install, the more sensitive they will be to tuning needs so if you try to "layer" back the tuning by playing with the mechanical then dynoing and then adding the tune to see what each gives you, it wouldn't be an accurate comparison to your previous setup.

 

your vtec is set too low, the cams are going to be totally different and need tuning im suprised you hit 184 without tuning and just a chipped ecu with the bc3+

get on a dyno and tune the a/f timing and cam gears to see max potential on the dyno then go on the street to tune for driveability an gas mileage

 

What are the degree specs for these BC4's? Does anyone know?

 

if u go to the buddyclub site there are the centerlines...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by coptzer &raquo;</TD></TR><TR><TD CLASS="quote">your vtec is set too low, the cams are going to be totally different and need tuning im suprised you hit 184 without tuning and just a chipped ecu with the bc3+

get on a dyno and tune the a/f timing and cam gears to see max potential on the dyno then go on the street to tune for driveability an gas mileage</TD></TR></TABLE>

The engine was indeed tune to specially run the BC3+ on my B18C5 engine. It was custom tune by J's Racing Japan for endurance racing for my setup and they wanted my engine to run on the rich side cause its 12hrs endurance road race and track temperature is very high here.

Just wanted to see how the BC4 will run on a tune that was made specifically for my previous setup. And since i now have a S300J, so thought i might as well get a new tune with the BC4 too.

I was also going through some old search files and did find people running the BC4 as low as 4800rpm like Tbone. Hope Tbone chip in on these.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by db1love &raquo;</TD></TR><TR><TD CLASS="quote">What are the degree specs for these BC4's? Does anyone know?</TD></TR></TABLE>

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by chris_tune &raquo;</TD></TR><TR><TD CLASS="quote">if u go to the buddyclub site there are the centerlines...</TD></TR></TABLE>

Yes i know the website has the center line. I have the cam card too which i had said i had degree them to spec at 102 / 104. And this spec are for vtec lobe and somehow it didn't run too well.

So does anyone has the primary or non-vtec lobe center line will help

Cause i might want to test and degree them again on non-vtec lobe.

 

I got my mech to degree the cams again yesterday with vtec lock etc. Put everything back, warm the car up and test drove the car. Suprisingly there is no more bogging or mis-fire issues on vtec transitions. strange..

The only thing now is during gearshift, the car would pop once on re-acceleration.

As my wideband is dead now, i can't see my a/f and was not keen in revving high on my initial run test. Trying to get my car to the dyno next week to see what the power and torque on these BC4 cam settings.

Thanks everyone who had chip in or help me in anyway or pm me suggestion and guidelines

Thanks.

Chris