vidanator

I have a "regular" tube size header for my 1.8l, its a high tech replica which i know numerous people have also used. I know that is not the problem, so i think going to a full 2.5 would defintely help, and defintely also adjusting the cam gears. Not worried about having a high vtec xover, i just dont like it, my power band is way too low before 8000, gonna post my dyno graphs tomorrow, i would really appreciate everyones input.

DDTECH

suck it up and drop vtec if you dont like it.. dunno what to tell you lol.

92cxturbo

I know you said you weren't gonna mess with it anymore, but you probally could pick some more power retarding you exhaust cam a few degrees. I know it didn't make any more power retarding the exhaust cam with the 4-1/stock cat, but thats cuz you had to much restriction in the exhaust. I just tuned practlly the same set as yours, 11.5:1 gsr, skunk2 s2 cams, IM, header, and 2.75 exhaust/no cat. The cam gears ended up at +4I, -1EX. With vtec at 5600 it was a nice smooth transition from low to high cam.

vidanator

Heres my current setup:

B18C1 block and head
pr3 .50 over
s2 s2 cams and valvetrain
blox im
comptech icebox
hytech 4-2-1 replica
highflow cat
rsr exmag 2.36
310 injectors
65mm tb

First dyno is my current setup with vtec set at 7200
Second dyno is old setup with gsr cams and jdm itr 4-1, with vtec at 5200

DDTECH

I know this much is true, you shouldn't make peak torque , before vtec..

vidanator

If its dropped any lower there would be a huge dip after vtec
Either way im going to get a full 2.5' exhaust, but would changing back to the jdm itr 4-1 header help with the dip and lowering vtec?

DDTECH

Whats up with everyone going these small piping.

Go 3'' - there's a ton of misunderstanding on this forum and the sub forums and i wish someone would sticky what i say.. because i hear all these guys making globs of power but wanna upgrade to a 2.5'' exhaust.

Go 3'' , You want more velocity flow not backpressure.. you want to create a tone that the exhaust flows too which creates sacavaging and THAT creates power..
Hell, if i could find something affordable i'd go 3.5''. Even bone stock b16's or bone stock gsrs gain massive power by going to 3''
I had 2.5'' on my itr motor for awhile, when i went to 3'', i had to add almost 15% more fuel across the board because the motor was producing power so much more efficiently..

Ditch the crappy headers your running... and get a good header..there's been alot of good numbers with the RMF knock narrow header, the smsp or the bishi headers aren't that much anymore go with something proven..
hell, get the new skunk2 header, thats probably more along the lines of what you need and it'll produce just about the same as a full custom header..

DDTECH

What i've understood and what others have shown me, is that a high vtec engagement point is due to poor engine breathing.. shitty header, shitty exhaust, stock cat, etc etc..

I "had" that problem on my b20vtec in my hatch, my low cam carried all the way to 7k.. so i set vtec to 6400rpms where it felt smooth.. but it shouldn't be that high. there's no cams on the market that require vtec anywhere above 6000 rpms.. unless your running vteckillers which vtec is on all the time.
From time and time again i've seen the biggest cams on the market like vtec in the mid to upper 5k range, even 6100rpms..but nothing higher..
You should never make peak torque off of vtec, that shows something is wrong whether its a exhaust problem or a internal motor problem.

DDTECH

On s2s2's the exhaust cam almost has to always be retarded to make really any power on those cams..this is coming from years of seeing different setups posted , the exhaust cam is always retarded like -2/3/4 degrees and the intake is always +3/4/5

I think you should go back.. and i think you'll thank us when you gain more power.

fungus mungus

00Red_SiR,
Keep in mind that while I had a big drop at the VTEC crossover when switching from the JDM ITR to the DTR, I gained 13whp up top (175-188). While going back to my JDM ITR will smooth out the transition, I'll be back where I was before.

ALL MOTOR,
I hear what you're saying, and things being different, I would certainly spring for the cut valve cover now and do a retune. But I've made a commitment to redo the bottom end (it burns oil in VTEC) within the next 2 months. Another tune now would be money wasted.

Thanks all for your help. For the other posters that are having a similar issue, I'm really curious how it works out for you.

fm

92cxturbo

I think your confused by what I said. The intake is advanced 4 degrees, exhaust retarded 1 degree. The op said his setting were intake +4, exhaust +3, and I was simply saying he should try to retard his ex cam some more.

DDTECH

oh no i understood you, was just saying lol..

92cxturbo

your saying what? I should advance the exhaust to +2?

DDTECH

No, i'm saying you should retard the exhaust to -2 or -3..

92cxturbo

oh, I didnt feel comfortable going more then 5 degree's of seperation cuz I dont have the v2v measurements, and its a gsr head. Plus it has 310cc injectors, and it was hitting 85% duty cycle at 60psi fuel pressure.

00Red_SiR

Right...which is exactly what would happen if you stuck a header that was meant for more displacement on your current engine... Understand what I'm saying? If that DTR header was meant for your current engine, you'd probably make similar gains in the top end WITHOUT the big drop at the cross over. Custom headers work very well which is why they cost what they do but they are often designed to work on a very specific engine build.

fungus mungus

Understood...in a couple of months, I should have a build that the DTR header will work well on.

vidanator

I think i'm going to give the 3" exhaust a try with no cat, who knows, my cat could be a little clogged. Dont think i'm going to get a new header though, might switch back to the jdm itr 4-1 if people say the 4-2-1 is also causing the dip. Hopefully i'll get this done within a couple months also, thnks for everyones input.

fungus mungus

Just so you know, when I swapped to the DTR 4-2-1 and noticed the dip at vtec, I had deleted my cat as well. I doubt just removing your cat is going to work for you. A 3" exhaust...maybe. I'd probably go back to my JDM 4-1 (or get a custom 4-1) if I were planning on keeping my build as it is.

fm

vidanator

Yeah i hear what your saying. Just a little scared that my cat is a little clogged because i was running rich before. When i change my exhaust and take a look at my cat, if its fine i might leave it.

fungus mungus

Bringing my old thread back from the dead, but I thought you'd like an update. My build is going to take time, so I've decided to have another go at tuning on DSR's Dynojet. Here's the graph:



I'm encouraged by the results. Although VTEC is set high...6700RPM, the curve is very good. The red is the baseline (basically the same as it was in July when I tuned on the Dynapak) and the blue is the final tune at DSR. You can see a marked improvement in overall torque and that the problematic VTEC crossover cleaned up nicely. Gained 25 whp in that area alone.

To get the tune to this point, we had to raise the VTEC crossover, add fuel (it was running a bit lean), and add advance the intake cam gear to +6. Lawrence wanted to do more with the cam gears, but since the cams were never degreed when they were put in, we decided against it.

He did say that he thought the reason VTEC wanted to be that high is that my exhaust needed to be bigger...at least 2.75" to take advantage of that header. I'll consider that option for the future, particularly when I go with an 84mm build, but for now, I'm happy.

fm