Long story short:

stock b18c5 longblock

A couple of years ago, I made 191whp with JUST toda spec b's and i/h/e + vafc.

Then I went to spec c's, and with i/h/e baselined at 186whp without any cam gear tuning. I figured that setup would be close to the b's or surpass it in the upper rpm band, but didn't worry too much about it because I had other things in store.

Fast forward to yesterday - the only thing I changed was the addition of toda itb's.

Dyno'd 170whp! W T F !!!?

This was on crome with tps baseline tuning, but something is amiss.....
We didn't touch the cam gears because I want to figure out wtf is wrong before going any further.

I was trying to do a back to back comparo of plenum vs itb's, but obviously something is very wrong..... I didn't expect astronomical gains, but to net such a loss is quite disconcerting.....

Here are the only things I can think of that may cause the loss of power:

- I changed the timing belt recently (triple-checked it).

- I ground down the underside of the rocker arms for additional clearance.

- I replaced the portflow Ti retainers with Rocket Ti.

- The itb's were purchased from King Motorsports and were "ported" by them prior to my purchase.

- I was using a hondata IM gasket, and continue to do so.

- This motor has seen over 11k twice. No ill effects were noted. Valve lash was unaffected.

- ?????!

 

Damn man, thats wierd. Any gains in midrange??

 

Well you dont want to hear it ken but:

QUADRUPLE CHECK TIMING BELT

It seems to me like you are having a flow problem, it should not be dying off like that in the upper RPM range. something is not right, either timing or flow IMO.

Contact DONF

 

Whats your compression ?did you try fiddling the cam gear at the dyno ?

 

have you done a compression or leak down test?

 

After that, we did a compression test and they were all withina few psi.....

I'm planning to do a leakdown test again, and quadruple check the timing belt + valve lash.....

It feels peppy as hell... I just don't know why the output is fux0rd.....

 

take it to the track?

maybe your dyno is lying

 

My vote is with the baseline. How does the car feel?

PM me and I'll feed you my baseline. Its for a 2.0L w/12.3:1 compression and ITB's, but who knows, it might work for you.

 

maybe adjusting your gears will make all of your power back...Being that engine is healthy as can be..

 

you need to datalog both the plnum run at 186 then the itb run at 170 ... check the timing maps used, i;'m assuming the TPS was different for both runs and varying voltage will use varying timing and fuel maps ... the map sensor signal should also be checked.

totally sounds like ECU causing the difference to me ...

also what was a/f like for both runs ?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CHEETAH &raquo;</TD></TR><TR><TD CLASS="quote">you need to datalog both the plnum run at 186 then the itb run at 170 ... check the timing maps used, i;'m assuming the TPS was different for both runs and varying voltage will use varying timing and fuel maps ... the map sensor signal should also be checked.

totally sounds like ECU causing the difference to me ...

also what was a/f like for both runs ?</TD></TR></TABLE>


a/f was identical. timing maps were comparable.

the other weird thing is that the idle was set at 800 rpm in the ecu, but the itb's started idling at 1400rpm...

 

Also, take note about the weather. Humidity, heat, barometric pressure, all these will affect an all-motor car IMMENSELY!!! You might not be down on power, it might just be a little hotter and a little more humid than the last time you dyno'ed!

Just a thought, I have had it happen to me numerous times!

 

Timing belt off a tooth, not getting full throttle, ignition maps fuxored, VTEC not working. You have something seriously out of whack. Good luck figuring it out, it should be a killer when the bugs are squished

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Black R &raquo;</TD></TR><TR><TD CLASS="quote">


a/f was identical. timing maps were comparable.

the other weird thing is that the idle was set at 800 rpm in the ecu, but the itb's started idling at 1400rpm...

</TD></TR></TABLE>

vacuum probs? have you checked all your voltage at the sensors?

 

I had a similar problem on my itb's a while back. Turned out that the throttle plates were only opening 3/4 of the way. Confirm that you are getting 100% throttle with them. I went from 185whp to 230whp after fixing the throttle cable issue.

 

.....here's the graph:



(blue line = itr motor + spec c's and itr IM + TB)

(red line = itr motor + spec c's and toda itb's)

Both are baseline tunes for fuel and have no cam gear tuning (0,0).

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GoldenEagleMfg.com &raquo;</TD></TR><TR><TD CLASS="quote">Also, take note about the weather. Humidity, heat, barometric pressure, all these will affect an all-motor car IMMENSELY!!! You might not be down on power, it might just be a little hotter and a little more humid than the last time you dyno'ed!

Just a thought, I have had it happen to me numerous times!</TD></TR></TABLE>


yep, he's 100% right. the last time i dyno, i only put down like 172hp at the wheels. didn't make sense since the motor put down more before a week earlier. same dyno, only difference was the weather, that day i dyno after it got done pouring. usually for us, after it rains, its hotter and more humid

 

i think you have throttle issues and timing problems

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Black R &raquo;</TD></TR><TR><TD CLASS="quote">
the other weird thing is that the idle was set at 800 rpm in the ecu, but the itb's started idling at 1400rpm... </TD></TR></TABLE>

do those itb's allow you to pre-set the throttle plate gap before mounting 'em onto the motor? if it's flowing too much air at idle, you'll never get the rpm turned down... and toda itb's are pretty big for a stock b18.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by danimal &raquo;</TD></TR><TR><TD CLASS="quote">do those itb's allow you to pre-set the throttle plate gap before mounting 'em onto the motor? if it's flowing too much air at idle, you'll never get the rpm turned down... and toda itb's are pretty big for a stock b18.</TD></TR></TABLE>

Yeah, I can play with the throttle plate stopper set.




I double-checked the timing belt today and valve lash. The timing belt seems to be dead-on. If it's off, it's only by 1/2 a tooth at the crank and not at the cam gears... which I don't know if it's even possible. I put the belt on the crank, then the cam gears, then the tensioner and water pump pulley's... I do remember that the helms says to do the crank, then tensioner, then cam gears - but the way I did it lined it up a bit better.....

Perhaps vtec isn't engaging? I just don't know anymore.....

I guess I can redo the timing belt again - but honestly, I think I'm just going to take it up to Jack at p1 and let him **** with it. This **** just don't make any sense.....

 

different dyno maybe? 191 whp is pretty hard to believe with stock bottom end and cams. i think your older dyno visits were higher numbers than they should be, and now you are realizing more realistic numbers. whop tuned it? if you can send me the crome bin file, and a graph of your air/fuel ratio, i could send you a couple different bin's to try. what kind of timing are you running? whats the air/fuel doing?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">- The itb's were purchased from King Motorsports and were "ported" by them prior to my purchase.</TD></TR></TABLE>
Might be the porting too... Too big ITB's cause airflow inconsistency and will actually harm performance rather than gain it. That said, pick up a book on TBI and tuning it, speedpro should have something along the lines on their selection.

 

I think your problem is with your actual compression ratio.
For example many ppl using skunk 2 stage 2 cams in a stock gsr motor complain of loss of power. This is due to the fact that the 10.1:1 compression ratio is not enough compression to support such an aggressive cam set up.

Now with your case you have a b18c5 which is a 10.5:1 ratio. You made the most power with the spec b because they are not as aggressive as the spec c cams. The spec c cams would work much better if you bumped up the compression ratio of your motor. you can do this by different pistons or a smaller head gasket. This is also probably your reason for losing even more power with your ITB. ITB require a high compression ratio to acheive any horse power gains. so you might want to look into some high compression pistons or change to a high compression head gasket.

Good luck

 

Toda's are 50mm correct? Do you have any idea what they are bored to? 52mm is ideal for 2.0L high compression. 50mm is ideal for 1.8L high compression, and 48mm is ideal for mild 1.8L builds. This of course is assuming the runner length and velocity stacks are ideal.

I would be concerned that the ITB's are simply not providing enough air velocity for your application. With the Toda C's on stock ITR bottom end, you are bleeding off a lot of compression with the overlap on the C's, your dynamic compression is much lower than with stock ITR cams.

Try advancing your intake cam as far as you can w/o P2V contact, this will help limit the amount of compression the cam bleeds, and might give the ITB's enough air to scavenge and create a bit more velocity.

You can try messing around with the ignition timing a bit, but you are fighting an uphill battle until you give that motor a bit more compression to play with.

 

next check the thr plates = with motor off, have some floor throttle, you try to look into each thr plate and make sure they are straight "flat" and not at an angle or well you'll lose alot of power.