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Larger Throttle Body causing increased breather pressure??



banhama

ClioSport Club Member
This is in my 182 track car.
While the engine was out I polished the manifold tracts and did my best to match the ports on the 2 intake sections and head. I also cleaned up the exhaust ports and internal welds on the exhaust manifold.
I then fitted a 62mm throttle body, calculating that it gives about 14% increase in TB intake area.

I honestly did not expect this to have any effect on the car at all, just something to do over the winter.
Pretty much all the knowledge on here says larger TB has no effect, as the manifold tracts are the limiting factor, and polishing/porting really doesn't do much.

I have since done 3 swaps from 62mm TB, back to 60mm and back again etc. And I am pretty sure there is a small performance gain in the 62mm TB. Better response at low rpm, which is giving a better corner exit and a couple of mph top speed gain down the tiny straights at Lydden Hill. The result being around 4 tenths quicker laps, very worthwhile. I'm afraid I only have lap times and data logging as evidence, no dyno readings.

Anyway it has a bit of a downside in that when the 62mm TB is fitted the breather pressure or volume seems much higher.
This first showed itself by blowing the dipstick out and covering the front of the engine with oil! It then blew the crankcase breather pipe off the connection at the rear of the engine and giving that a good coating.!
Running the crankcase breather to atmosphere via a catch tank has cured this.

The rocker cover breather now seems to be a problem.
The tiny hole that blows into the intake manifold is difficult to seal with the weird gasket. It relies on the manifold having no deformation or slight warping, otherwise when you tighten the bolts on the front of the intake you are lifting the breather seal at the rear.
So this has manifested itself by venting oil onto the rocker cover, filling the first spark plug well and causing a misfire!

Put the bloody 60mm TB back on and have done with it I hear you say!
But having convinced myself the 62mm TB offers a few tenths that would be defeatist.

So how do I vent the rocker cover to the catch tank, while keeping the OEM intake manifold.

Thinking of doing something with the oil filler cap, like making one with a hose connection.

Any thoughts welcome
 

banhama

ClioSport Club Member
That would be ideal, but I'd have to take some advice on where to make the hole, and there's not much of the top of the cover visible, but if anyone has done exactly that I would love to see pics please
 

NorthloopCup

ClioSport Moderator
@banhama have you had it mapped on the bigger throttle body? If you haven’t I’d suggest you get it done. The engine is showing improvements in airflow as it’s potentially increasing the manifold pressure. It may well be drawing more air in, but unable to burn it.
 

banhama

ClioSport Club Member
@banhama have you had it mapped on the bigger throttle body? If you haven’t I’d suggest you get it done. The engine is showing improvements in airflow as it’s potentially increasing the manifold pressure. It may well be drawing more air in, but unable to burn it.

I haven't had it mapped on the bigger throttle body Mark, but that has been nagging at me so yes, bloody good idea! Sometimes I just need someone to tell me to do it!
I currently just have the RSTuner 98 Ron map, I will contact RST to see if they have an off the peg map for a 62mmTB, but I doubt it. So it looks like I should be trailering to a reputable mapper in the southeast with a dyno. Any recommendations?

Many thanks for your help.
 

banhama

ClioSport Club Member
I hadn't noticed this when I cleaned the oil out of the spark plug well and re-fitted plug and lead.
The car started missing again and no wonder!!

I guess that when the well was full of oil the spark tried to divert through the oil, eventually blowing a hole through the rubber.
It must have either burnt away the socket in the lead that fits over the plug terminal, or blown it back, as when you fit the plug it there is no contact with the socket.
The second photo is with the plug pushed fully into the lead, but there is still a gap where the hole is.

This is my amateur explanation, but I would welcome any other ideas

20210630_163211.jpg


20210630_164645.jpg
 


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