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After installing skunk stage 2 tuner cams on 12:5:1 B18C5 / Integra Type R I am experiencing a big drop in Air flow from 6000-7000rpm

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Hi fellow racers and engine builder’s ,

Before I put the skunk Stage two tuner cams and ported head on my B18C5 I had no dip in air flow after VTec and a power band with no dips or valleys. I Installed the cams using the factory TDC timing marks . I did not degree the cams . On the dyno it made the most power with the both cam gears advanced +2°. My VTEC is engaging at 5500 RPM but at 6000-7000 rpm the air flow just falls off and then picks back up at 7000 till redline.

Could it be cams are out of phase/ timing, or to much overlap causing loss in compression or the scavenging affect is lost??? Has any one else encountered this issue with cams or Honda bseries motor??

I will attach my hondata air/fuel map we’re you can see the drop in VE /air flow and I will attach my dyno chart.

Attached Files

On na motor it well could be your exhaust header geometry making significant impact on power/torque curve... Getting extra power from na motor requires more details to be looked at as a whole picture. Intake manifold geometry, head porting, intake channels size, valves size, intake to exhaust valve size ratio, compression ratio, exhaust channels size, exhaust header geometry - it should be calculated well before putting it all together as every single one of them can have an impact on final result... Especially with ported head and big cams where the power curve highly depends on intake air charge velocity, so putting it in tact with exhaust pulses should be very well pre-calculated...

Hey Georg1970,

Thanks, for the response

Here are my engine specs and parts

Engine specs for B18c5 / 98ITR. 91octane 208whp 135tq

Skunk 2 Tuner 2 cams

Stock bore CTR pistons with milled Type R Head =compression of 12:6:1

Type R rod’s and crank.

ported and polished head

Supertek springs and retainers and valves stock size

skunk 2 Ultra St. manifold with 74 mm throttle body

550 cc alpha injectors fuel regulator 60 psi

skunk 2 cam gears both In&EX@+2 advanced

DTR TRI-Y race header

72mm-76mm TestPipe

76mm skunk 2 megaRR exhaust

3inch I.D. Custom cold air intake with velocity stack

I will attach a video of the Dyno run

Attached Files
  • trim.A2D58530-49F8-40FF-ACB7-B365CE2A5299.MOV
  • Attachments may only be downloaded by paid Gold members. Read more about becoming a Gold member here.

This is why people run engine simulations. Nobody can take a look at your parts list and tell you what to change to fix your problem. You could build a dozen different exhaust systems with different tube diameters and primary / secondary lengths, merge angles and test them (that's how older engine builders did it and learned what worked and what didn't for a given head/cam combo). Or you could simulate that (and different CAM timing, valve lift, etc) to find a combination that comes close to what the factory engineers did in the first place -- a smooth even torque curve across the power band.

Do you have any links to or names of a good simulator for me to use?

I use Engine Analyzer Pro. The other good simulation programm is called Lotus.

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