Performance drops after porting

[Prince1984]

Hello all,

After porting work, the performance of my car drops except in the low 2200 rpm or lower. Above that mark, torque dan hp drops. In fact, in the rpm 4500-5000, they drop significantly (proved by dyno tests)

No other mods I use except the knn air filter panel.

If it is because of the porting, as I suspect, can you all help tell me the causes of the drops? Tx.

 

[boyan]

hi im wery interesting what car are we talking about?and if you have any
photos to post cause im heading in this direction! am porting a jaguar
6 cylinder 24 valve....boyan

 

[T9 man]

Greetings and a Warm Welcome to our TorqueCars Forum my Friend!

Good to have you along with us

 

[HDi fun]

It's possible that you can get performance drops after porting if you reduce the turbulence in the intake tracts. Turbulence is important to get proper air/fuel mixing. In general though you'd lose out at the bottom end rather than higher up so this situation is unusual.

 

[Prince1984]

Its a small car, toyota yaris/vitz.

It's possible that you can get performance drops after porting if you reduce the turbulence in the intake tracts. Turbulence is important to get proper air/fuel mixing. In general though you'd lose out at the bottom end rather than higher up so this situation is unusual.

some info I get mentioned that perhaps the exhaust ports were ported relatively smaller than the intake ports, causing the resistance (or back pressure?) especially easily noted in the higher rpm when air flows more and faster. Any thoughts?

Also, it is easier to increase the speed when I increase it slowly instead of kicking down. When kicking down, the rpm stops to increase when it hits 4500-5000 in the final gear. In the lower gear, the rpm still can go up to 6500-7000.

My thinking agrees with the back pressure idea. but I need to have more inputs before porting more the exhaust ports.

 

[MasterAuron]

Flowing a head properly is a dark art and whomever carried out the work doesn't know what they're doing, clearly.

Speak to Ric Wood at CNC heads or somebody else that can carry out the work successfully if you're not in the UK.

 

[obi_waynne]

The 3 or 5 angle valve job angles are just as important IMO as the overall flow rates and angles. I've often heard of performance drops, wider tubes flow slower than narrower ones. My aim in porting and flowing is to minimise the bends and allow for a swirl into the combustion chamber. Most porting pushes the power band higher up the RPM range leaving a car gasping for low down torque. As MA says it is a dark art and best left to the pros on a proper flow bench.