Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head
03-29-2005, 05:49 AM
#1
Honda-Tech Member
Thread Starter
Join Date: Apr 2002
Location: Montreal, Canada
Posts: 846
Likes: 0
Received 0 Likes
on
0 Posts
Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head
I went to the dyno yesterday and did a few runs with my road race car. My setup is the following: B18c1 block, b16a head and cams, head is ported and polished. After playing with the timing, we managed to get the hp up to 141 hp, but that was it. At 6600-6700, it starts to drop off very sharply. We didn't have time to setup my exhaust to accept the wide-band before the cat, so that's all the info I have for now. Does anyone have any idea what could be causing this? One of the mechanics at the shop suspected I might have cams from an automatic B16a. I wonder if the air-fuel ratio could affect high rpm hp so much or am I somehow at the limit of these cams. Any ideas?
03-29-2005, 09:03 AM
#4
Honda-Tech Member
Re: (Civic44)
eeww why are you even using b16 cams? its ok to use a b16 head but at least get some gsr cams in there, b16s are too weaksauce, about your power dropping off that sounds weird should climb to at least 7800, any dyno charts?
03-29-2005, 09:14 AM
#5
Honda-Tech Member
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (Civic44)
no way to really know without your a/f curve. Get it straightened out and go back.
s
s
03-29-2005, 10:09 AM
#6
Honda-Tech Member
Thread Starter
Join Date: Apr 2002
Location: Montreal, Canada
Posts: 846
Likes: 0
Received 0 Likes
on
0 Posts
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (stevel)
I didn't get the charts printed out, I'll try to get them. I only used B16 cams because that's what I had. I didn't know that they would hinder performance...
03-29-2005, 11:06 AM
#7
Honda-Tech Member
Join Date: Nov 2004
Location: 40.201N, 77.189W, PA
Posts: 4,738
Likes: 0
Received 7 Likes
on
4 Posts
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (Civic44)
The B16 cams aren't any worse than the GSR cams for power. Virtually the same profile I thought.
Trending Topics
03-29-2005, 11:41 AM
#8
Junior Member
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (HondaBullSQ)
if he has the obd0 first gen b16 cams then its a different story, especially when its automatic (yes they are different specs).
who ported the head? did he provide you with a cfm chart before and after?
who ported the head? did he provide you with a cfm chart before and after?
03-29-2005, 12:37 PM
#9
DYNO-PRO
Join Date: Mar 2004
Location: SoCal I.E 909, CA, where we innovate not immitate
Posts: 4,392
Likes: 0
Received 0 Likes
on
0 Posts
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (c17r15)
please post the dyno chart because if it is dropping off as violently as it sound then the car may be falling out of vtec due to an oil problem ..
03-29-2005, 12:46 PM
#10
MEAT PATTY
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (HOOKUPS)
Like Hookups said ^. Stock b16 cams stop making power at 7600 and b16 and gsr cams are almost virtually identical their is no noticable hp increase between the two of them. You might have automatic b16 cams though. Need to post the chart up or let us know what the air fuel was across the board. Might have to bust out microsoft paint and get creative. 
03-29-2005, 04:05 PM
#11
Honda-Tech Member
Thread Starter
Join Date: Apr 2002
Location: Montreal, Canada
Posts: 846
Likes: 0
Received 0 Likes
on
0 Posts
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (goforbroke)
Yeah, I guess I have to do some more runs with the wideband, we didn't have time to set it up. I'll also try to get them to email me the chart. Thanks for the ideas so far.
03-31-2005, 08:15 AM
#12
Honda-Tech Member
Thread Starter
Join Date: Apr 2002
Location: Montreal, Canada
Posts: 846
Likes: 0
Received 0 Likes
on
0 Posts
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (Civic44)
Here's the dyno chart. As you can see, after 6500, it's all downhill:
03-31-2005, 08:29 AM
#13
Junior Member
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (Civic44)
whoa.....that doesn't look right, I've seen 2L blocks on a stock auto pr3 head, the power doesn't "drop" per se instead it sort of flatten itself out and drops.
it sure could be a dirty head where the engine can't breath past 6700 rpm.
it sure could be a dirty head where the engine can't breath past 6700 rpm.
04-01-2005, 12:49 PM
#14
Member
Join Date: Sep 2003
Location: Texas Damnit
Posts: 1,569
Likes: 0
Received 0 Likes
on
0 Posts
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (Civic44)
might be the header you're using. I've seen dyno charts that show a DC JDM 4-1 fall flat on its face after 6500.
04-01-2005, 12:55 PM
#15
Honda-Tech Member
Thread Starter
Join Date: Apr 2002
Location: Montreal, Canada
Posts: 846
Likes: 0
Received 0 Likes
on
0 Posts
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (DavidR)
Could it be my "high flow" aftermarket catalytic converter then? I have a JASMA 4-2-1 header (don't know the brand) with a 2.25" exit, 2.5" piping, high flow cat and Cherry Bomb Turbo muffler.
04-01-2005, 01:04 PM
#17
DYNO-PRO
Join Date: Mar 2004
Location: SoCal I.E 909, CA, where we innovate not immitate
Posts: 4,392
Likes: 0
Received 0 Likes
on
0 Posts
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (DavidR)
correct me if i am wrong but that dyno plot is not in RPM it is in "SPEED" 
04-01-2005, 02:56 PM
#19
DYNO-PRO
Join Date: Mar 2004
Location: SoCal I.E 909, CA, where we innovate not immitate
Posts: 4,392
Likes: 0
Received 0 Likes
on
0 Posts
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (rev limiter)
this is a very odd looking dyno plot i dont think i have ever seen this type of dyno
04-02-2005, 06:07 PM
#20
Honda-Tech Member
Join Date: Oct 2002
Location: chillin in that city called queen creek, but homes the atl
Posts: 3,518
Likes: 0
Received 0 Likes
on
0 Posts
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (HOOKUPS)
i'm so supprise that no one mentioned that his vtec is not working thats why his power falls to a dead stop at around 7 grand. plus that graph makes no sense
04-02-2005, 09:03 PM
#21
Honda-Tech Member
Thread Starter
Join Date: Apr 2002
Location: Montreal, Canada
Posts: 846
Likes: 0
Received 0 Likes
on
0 Posts
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (street dreams)
The vtec is coming on, I can hear it and I have the runs on video and I can hear it when I watch the video too.
04-03-2005, 06:47 AM
#22
Honda-Tech Member
Join Date: Oct 2002
Location: chillin in that city called queen creek, but homes the atl
Posts: 3,518
Likes: 0
Received 0 Likes
on
0 Posts
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (Civic44)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Civic44 »</TD></TR><TR><TD CLASS="quote">The vtec is coming on, I can hear it and I have the runs on video and I can hear it when I watch the video too.</TD></TR></TABLE>
i dont think so buddy low fuel pressure is not going to make your power fall off at 6700 rpms u have no vtec
i dont think so buddy low fuel pressure is not going to make your power fall off at 6700 rpms u have no vtec
04-03-2005, 05:37 PM
#24
FSAE
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (EFB16ACRX)
You might have auto-b16 cams, which are rated at around 150hp stock (instead of 160 for the 5spd).
04-03-2005, 06:38 PM
#25
Honda-Tech Member
Join Date: Nov 2001
Location: georgia
Posts: 2,484
Likes: 0
Received 0 Likes
on
0 Posts
Re: Why does my power drop off so sharply at 6700 rpm - B18c1 block + B16a1 head (92TypeR)
whatever that **** sucks
as most will say theres some sort of "breathing"or fuel problem withthe motor.
list out all your mods so we might be able to help u figure it out, and also try a normal dyno next time
i made 157whp with a bone stock internals b16 so u definatly have an issue
as most will say theres some sort of "breathing"or fuel problem withthe motor.
list out all your mods so we might be able to help u figure it out, and also try a normal dyno next time
i made 157whp with a bone stock internals b16 so u definatly have an issue