Mazda Rotary Club

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

Help would be appreciated

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.

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...

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

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.

Cheers, that answers the question:)

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? :D (rear seats to make way for 300 litre fuel tank then!)

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

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.

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

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!:(

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.

Yes,
Kind regards
Carl

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!! ;)

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

?

QuoteOriginally posted by 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

I would like to add that Geff was like many of us limited in time and resources on working on this project and no doubt in the future he will vastly improve on his own engine.
The engine too inspite of not blowing up is a litle tired and a bit smokey so is to be pulled down and looked at.
I got one figure wrong,at totb 2 Geff did 174mph not 176mph.
Kind regards
Carl
:)

All i am saying is that on the subject that, I do not think you should be all secretive about your bridge porting, be secretive when you have a powerful car, bridge ported cars should be much faster.
Where I used to come from, if you have a bridge under the hood, you have a very very quick car.
You say, it was not tuned by you, was it tuned bad? how would you have tuned it?

Quote bridge ported cars should be much faster.
Where I used to come from, if you have a bridge under the hood, you have a very very quick car. [/B]

QuoteMy point exactly,as I only built the engine it is my prerogative if I do not wish to disclose what I have done internaly,so the fact that this car should be quicker is not down to the engine.It is down to the fact that neither the time or resources were spent on it externally due to work constraints.The turbo has been recognised as not ideal as it could not keep up with the porting in that the boost was dropping at revs.

you say, it was not tuned by you, was it tuned bad? how would you have tuned it? [/B]

I had nothing to do with the tuning and once again it was tuned in a very short time due to time constraints,which  limited the engines true potential.
One other point is that this car was to do 3 entirely different events at totb which also mean that it must be balanced for these events,for example it had a differential ratio in it that  compromised the 1/4 mile in favour of the high speed run,so if only the 1/4 mile was concentrated on just in that one area alone the car would have been quicker.This is just one example of where things could have made the engine look less than it is.Instead the high speed run was reasonably good.

Claizy,what was the standard engine running(That did the 12.66 1/4) with regards to turbo?Intercooler?Injectors?Diff ratio?Fuel?ECU?

Kind regards
Carl
:) :wave

QuoteOriginally posted by Carl
Claizy,what was the standard engine running(That did the 12.66 1/4) with regards to turbo?Intercooler?Injectors?Diff ratio?Fuel?ECU?

Big f#ck off Apexi AX75 single turbo.
Apexi  GT-spec FMIC.
Dunno.
Stock.
Dunno.
Power FC.

Hi Rich,
are you referring to Ross\'s car?
Kind regards
Carl

No, the guy was talking about the montego blue FD that ran 12.6? at TOTB2 on the same day geff ran 12.37 - I think???

Guys name is Russell.

If that is so then what was the high speed run for Russells car?
Kind regards
carl;)

Who is Claaizy?  Must be someone we know?  :)

.ps Street/mild port for sure.

Bridge port is a little to Claaizy for the street I think (I should know I drove one (non-turbo) for a few years!).

But bridge ports etc. are great value at the same time - a nice weekend car.

Russells car has 6 injectors, and used standard fuel, the weekend before TOTB chris fitted the injectors and we had about 1.5 hours mapping time(most of this was taken up checking the car) in the rain trying to sort everything out, then on the Wednesday about 2 hours. This car was by no means the finished article.
His car broke 5th gear on the first high speed run, it must have been all that power:D
It also has proper street tyres.

Jason

Hi Jason,
well in view of the circumstances that was a pretty good effort,we need to keep it up though cos the Skyline boys won\'t be sitting on their hands.
Where is the car now?What has been done to improve it?
How do you know the engine is stock?
Kind regards
Carl:wave

Russell still has the car, it is still going strong, their are still quite a few things with the car that are not within parameters I like to see, so it is a very safe tune as it survived a 1.5 bar spike.
I have promised to go and see him soon, just been busy of late.
Carl, Ross\'s car was 2.9sec faster on a 100-140 run, the power tailed off at the top end on Russells car compared to Ross.

Jason

PS. Chris built the engine last year, with no porting.

QuoteOriginally posted by JayDee
Russell still has the car, it is still going strong, their are still

PS. Chris built the engine last year, with no porting.

Hi Jason,
You will find that Russell\'s engine was built by Tim at Rx Motors.
Kind Regards
Carl