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Could the supercharger be adding boost into the vacuum booster, thus rendering the booster non-functional? I know other boosted (turbo/supercharger) vehicles go other directions from vacuum boosted brakes.
It's really tough to ruin the oem Brembo calipers. I have tried alot of street and track pads over the years on my oem brakes and my brembo brake kit. Every time i had to use more force on the pedal was because either the vrakes werent properly bedded or the pads just didnt have enough bite. I would consider saving some money on calipers and try a more aggressive set of pads.
True, but he ìs speaking of his engine swapped E30, not of a 996...
That’s the steady idle number, goes up a tick with revs. Engine is an S50 out of a 95 M3, I rebuilt it before putting back in. Supercharger is a newer addition.
For typical daily use, they are fine, but panic stops really become panic stops as the brakes absolutely will not lock up. It’s like they’re about 80% effective under heavy load. I’m not a small dude so it’s not my chicken legs!
That is typical of a booster not suited to the brake system and/or the vacuum provided by the engine.
They all have a spot in their boosting characteristic where, from a certain pedal effort upwards, they do no longer increase boost.
It seems like that pressure is lower on the Porsche booster you used to replace the BMW booster, it originally had.
Also, since it's smaller it has less reserve vacuum (i.e. it's s used its vacuum after eight instead of 10 [arbitrary numbers] full brake applications with engine off). Add to this, that an ITB equipped engine has less vacuum and more so off-idle and it becomes understandable that pedal force increases substantially to lock front wheels on high-friction surfaces.
Last edited by hardtailer; 06-14-2024 at 05:11 PM.
As long as we're on brakes, I just had new pads and rotors installed a few hundred miles ago, and I still have a slight 'squeaking' or scratching sound when rolling. Is this normal during break-in, or are my calipers not fully releasing?
Worth it's own thread, maybe? But it literally sounds like pads/calipers are not releasing and a replacement of (at least) the square seal in the caliper could resolve that.
OP: get rid of the ceramic pads and put in some normal ones, that don't claim to be dust free whilst at the same time avoiding any 'fast street' or track pads.
Last edited by hardtailer; 06-15-2024 at 03:15 PM.
Cheers for showing interest!!!
That’s the steady idle number, goes up a tick with revs. Engine is an S50 out of a 95 M3, I rebuilt it before putting back in. Supercharger is a newer addition.
For typical daily use, they are fine, but panic stops really become panic stops as the brakes absolutely will not lock up. It’s like they’re about 80% effective under heavy load. I’m not a small dude so it’s not my chicken legs!
Well, like said above, you seem to have it covered pretty well... As 18"i at idle should be 'adequate. What I don't understand is, you say with some rpm the vac goes up,,, on a boosted engine..? iirr, on a boosted engine under load at rpm there is no vac, hence 'boosted'. No..?
Don't super charger engines use check valves with big vac boosters or vac canisters..?
But you say it did work good originally with the swap and small booster..?
There's a couple different ways to deal with brake boost on forced induction.
G60 Corrados used an electrohydraulic brake system. No vacuum required.
Saleen Mustangs used a hydrauluc booster run off the power steering pump. No vacuum required.
996 Turbo as well as most turbo VW's use a venturi to draw a vacuum when under boost and some check valves to use manifold vacuum when the throttle's closed.
997 Turbo uses a camshaft driven vacuum pump.
Cayenne turbo uses manifold vacuum and an electric vacuum pump joined with check valves.
I'd suggest an electric vacuum pump to E30, and if that doesn't do it then a bigger booster - if possible.
I've had a few Porsches and the brakes are all awesome. The brake on my Panamera GTS are bad a**.
The brakes on my e30 have slowly gone to subpar and I can't figure it out. I bring this up because after I did the engine swap, I had to swap in a smaller booster from a Porsche due the size of the new engine.
Brakes wen't downhill, so .....
New fluid, no better.
I swapped in a new 7 series master cylinder as an upgrade, no better.
Went back to a brand new stock e30 master cylinder, no better.
Replaced the Porsche booster with a new Porsche booster, no better.
Removed the check valve, no better. (then bought a vacuum gauge, confirmed vacuum is adequate)
Rebuilt all 4 calipers, no better. even new bleed screws!
New sticky brake pads, no better.
Deleted the ABS pump and hard lined it, no better.
I'm now at a loss. Frustrating!
With an E30 you can just go to manual brakes to avoid a lot of hydraulics hassle - I was struggling with brakes in my race E34 until chucking the entire factory system and running new lines off an E30-specific twin-Tilton-MC pedal box. If you'd like to chat about it we can do PM's to avoid mucking up this thread.
Back to my topic
My original pads were Akebono Ceramic. I just ordered a set of Hawk HPS and will see if that improves things.
Now you are talking. I wasn't getting enough bite from my oem pads on my Audi S8 and went to the Hawks and it was night and day. More brake dust but I didn't care. Very good pads for the money.
2001 C4 cabriolet. My brakes are german rotors with ceramic pads, properly bedded. Redid DOT4 brake fluid with power bleeder so there is no air in the system.
For a while now, I've felt that my brakes were subpar. The shop that installed them and another I asked both shrugged and said "normal".
I remember the Audi crew used to use boxster calipers to improve braking, and I find it hard to believe my 911 brakes are this bad.
If you push down hard, I mean NOW, they stop, but it's like they have no power boost whatsoever. The same effort on my son's BMW 135i would put you in the windshield.
I don't think the master cylinder is bad, and there are no other signs of booster issues.
Suggestions? Maybe I should find someone local and swap cars for a quick run to compare...
I haven't changed pads/discs yet, so I can't comment, but there was another thread about pads that don't generate a lot of dust (https://rennlist.com/forums/996-foru...l#post19506843), and the consensus there seemed to be ceramics generally behave as you describe. In that thread, the Porterfield's sound like they walk on water -- no dust and but none of the issues with other ceramics. It might be worth looking through that thread.
06-14-2024, 03:48 PM
