Lowering VTEC
#31
Are you talking about just swapping the cat for a test pipe, no other changes, dynoing the car and comparing peak numbers? If so, I completely agree. A test pipe or HFC combined with lower VTEC could yield big gains in the midrange, even without and real tuning. I have a completely stock car with HFC, lowered VTEC engagement, and I just tuned it for healthy AFRs--haven't touched timing, and I saw almost 20whp more at 5900 rpm.
Yeah, I was just talking about swapping the cat out for a test pipe with no tune. Lowering VTEC regardless of anything else will have a big increase in the mid section. In my opinion the mid range is where you want the biggest gains anyway. I'm a little biased since I auto-x, but most of your time isn't spent at peak RPMs on the street anyway. Gernby had a nice write up awhile ago on how to tune out the VTEC transition to get a nice smooth powerband. If I can dig it up I'll post a link.
#32
Does the optimum lower vtec engagement point differ depending on the modifications you have on the car? I'm assuming that's why an e-tune or dyno tune is beneficial? Or is there a set number that everyone drops the VTEC engagement point to?
#33
It depends on some mods. I know that you can drop it much lower with a test pipe vs. the stock or HF cat
#34
There are some general rules of thumb. The way I understood it, you would be at the optimum once you get no spike in the dyno chart at the VTEC transition point (RPM).
#35
Originally Posted by Mocky' timestamp='1368192142' post='22532993
Does the optimum lower vtec engagement point differ depending on the modifications you have on the car? I'm assuming that's why an e-tune or dyno tune is beneficial? Or is there a set number that everyone drops the VTEC engagement point to?
#36
Originally Posted by Kermdaddy' timestamp='1368198633' post='22533246
[quote name='Mocky' timestamp='1368192142' post='22532993']
Does the optimum lower vtec engagement point differ depending on the modifications you have on the car? I'm assuming that's why an e-tune or dyno tune is beneficial? Or is there a set number that everyone drops the VTEC engagement point to?
Does the optimum lower vtec engagement point differ depending on the modifications you have on the car? I'm assuming that's why an e-tune or dyno tune is beneficial? Or is there a set number that everyone drops the VTEC engagement point to?
[/quote]
Can the datalog pulled from Flashpro identify this?
#37
Here is my dyno plot. Bottom thick red line is from a stock Ap2, thin red line in the middle is my car with Evans tune and 3900 rpm vtec, thick red line on top is my final tune done by UMS and vtec at 4200rpm. Notice the 5lb ft torque gain that was made by moving vtec from 3900 to 4200.
K&N FIPK, 70mm Invidia Test Pipe, Greddy Spectrum Elite Dual, Flashpro. 2008 CR
http://www.flickr.com/photos/41071623@N03/6834570008/http://www.flickr.com/photos/41071623@N03/6834570008/ by http://www.flickr.com/people/41071623@N03/, on Flickr
K&N FIPK, 70mm Invidia Test Pipe, Greddy Spectrum Elite Dual, Flashpro. 2008 CR
http://www.flickr.com/photos/41071623@N03/6834570008/http://www.flickr.com/photos/41071623@N03/6834570008/ by http://www.flickr.com/people/41071623@N03/, on Flickr
#38
I believe this mod should def. be done if you have a quality header/tp/non restrictive exhuast - 76mm...at least the TP / Header, no point in tuning and lowering v-tec w/o these mods first. You need to be able to move the air out quickly enough..first focus on the bolt-ons then the tune...the stock ECU is capable of handling the flow of the bolt-on w/o a tune. You will def. pick up a fair amount of ponies with a tune..I was told by realiable tuner, Jeff Evans that he can make 230hp for me with a K-Pro - stock intake, hytech header and tp and 76 mm exhaust.
#39
I've found the limiting factor in lower VTEC engagement to be exhaust flow through the cat. The better flowing the cat, the lower VTEC can be set. You can tell the cat doesn't flow as much as it needs by the AFRs going rich at the VTEC engagement point and not being able to tune this out. The dip in hp is a result of the AFR going rich. I think I've seen elsewhere that you have a HFC or test pipe(maybe you're considering one). If so, keep dropping the VTEC engagement point until you see richness at cutover on the flashpro datalogs that you can't tune out and raise it back a notch so you don't get the dip. Of course you don't want to go too low, but I'm not sure where that limit lies.
#40
I believe this mod should def. be done if you have a quality header/tp/non restrictive exhuast - 76mm...at least the TP / Header, no point in tuning and lowering v-tec w/o these mods first. You need to be able to move the air out quickly enough..first focus on the bolt-ons then the tune...the stock ECU is capable of handling the flow of the bolt-on w/o a tune. You will def. pick up a fair amount of ponies with a tune..I was told by realiable tuner, Jeff Evans that he can make 230hp for me with a K-Pro - stock intake, hytech header and tp and 76 mm exhaust.
Also depending on the year of the car (+02 and especially 04+) if you got some good bolt ons which provide a worthwhile increase in flow, the stock ecu will not accommodate the added fuel needed to support this. A TP is about it, beyond that you should plan on incorporating some measure of additional fuel, either from as simple as an adjustable fpr to turn up fuel pressure, to a full ems. Beyond about 13-13.5 afr you will be past lean best, run dangerously hot combustion temps and will start losing power. The factory ecu with cat puts the car in the 12's on years mentioned, a TP runs you near a full point leaner. You need a tune beyond that not just to maximize your gains, but to run safe.