Bridge or Street Porting

[Tickey]

Does anyone have any advise on whether bridge or street porting is best?

Help would be appreciated

[mr_tim]

Best for what? It depends on what power goals and driving you are after.

A street port will give good overall gains with little low end power loss so is very streetable.

A bridgeport will shift the power band up with larger gains at the top end but less at the bottom end.

[20B_boy]

The Bridgeport I drove for a couple of weeks (good few miles) was a bit of a ball ache to drive on the street, in traffic, cruising etc. It really preferred to be \'loaded\' all the time, otherwise it tended to buck about a bit, esp. around light throttle. Had solid engine and diff mounts too though which probably didnt help much

Not much at all below 4K, 5k+ and it hauled pretty well! Small-ish single turbo, twins would be different obviuosly...

Economy not too bright surprisingly!

Totally depends on what use your car will see...

[JayDee]

Rich,
I know it was half bridge, was the bridge full length of the port or smaller? I am considering bridging mine, put want to keep as much drivability for the better half.

Thanks

Jaydee

[20B_boy]

I\'m not 100% sure what you mean Jase; I only saw the plates very briefly - a long time ago. I think from recollection that:

a) only the secondary ports were bridged (hence \'half bridge port\')
b) the \'extra\' port created by the bridge was the full length of the \'main\' port...

Does that answer your question? If not, try again!

Carl will correct me if I\'m wrong I\'m sure.

[JayDee]

Cheers, that answers the question:)

[20B_boy]

So are you thinking of \'small\' bridgeports on all runners, or small ones in secondaries only or...?

Love the sound myself and would have one for sure. It\'s not like an FD is practical so you may as well go for broke

Single turbo\'d B/P 20B? (rear seats to make way for 300 litre fuel tank then!)

[bill shurvinton]

AS long as you know what you are letting yourself in for.

A little bridge does little more than ensure a poor idle and lousy cruise fuel economy for not much top end gain.

Whilst having an ECU with decent sequential injection setup can get around a lot of the issues, a partial bridge will still idle at 1500 and fail emissions if you need to take them.

On a turbo car it will drop the dynamic compression ratio considerably. Handy if you want to run 20PSI boost, a bad thing if you only run 14PSI.

Having said all that I do plan a bridgey in the westfield at some point.

Bill

[JayDee]

Just small on the secondaries, it depends where you place them to how bad the idle is:D
I know someone who has a 1100-1200 rpm idle, but then the top end increase might not be worth the trouble.

[Carl]

if youm want driveability then just do an extend port.I know that Rich has seen the ports but I am not willing to divuldge what I have done in The ReWorx RX 7 engine for Geff for obviuos reasons,this is a preety quick car.I will say that the turbo created some lag as the turbine is pretty big,hence the revs needed to get it going.
Kind regards
Carl

[20B_boy]

Sorry Carl, I hope I didnt say any thing out of turn; as you hid the trick stuff under a towel I presumed geff\'s plates were ok for public consumption! To be honest I wouldnt know the difference between a \'special\' B/P and any other B/P that I saw pics of unless they were side-by-side... I think most knew that the primaries werent BP\'d? Any way, sorry again.

Finally, I thought common consensus after TOTB2 was that the turbo was quite small? I forget how big the turbine hsing is exactly now though I have to admit.

T\'was a nice drive either way, shame I wont get to drive it again!:(

[Tickey]

Thanks for your replies.

I am fitting uprated twin turbos to my RX7 and I heard that street porting would be the best bet.  Does anyone agree with this?

I mainly use the car on the track.

Thanks.

[Carl]

Yes,
Kind regards
Carl

[claaizy rx7]

No disrespect, but I do not think that your bridgeported engine can be that \'trick\', as the car did a 12.3  quater compared to a stock ported car doing 12.6 on the same day!!

[Carl]

Yes but it was not tuned by me,and the externals were not carried out by me and did not have an ideal turbo on it,also it did do 182mph at the totb practice day and 176mph on the day.
Who\'s was the stock ported motor,Was it yours?Was it modded externally?
I have NO doubt that if the externals matched the internals it would have been much better,on top of that it has not blown up.
:p :p :p :p :p :p :p
lol kind regards
Carl