88 Turbo II , s4 motor with RA super seals
-- T04S 60-1 turbo (.96 undivided hotside, .70 compressor), HKS log manifold
-- 3" downpipe, testpipe, Racing Beat catback
-- did 386rwhp @ 18psi on 100 octane at one point (which is honestly kinda low...)
-- Power FC (self tuned), 720/1680, FPR, Greddy 3 row FMIC, basically every supporting mod needed for 500whp except the turbo

I pulled the motor the other day, for a number of reasons. I wanted to install an s5 rear iron and an oil pan brace, plus my clutch was almost done. I had also detonated the motor recently (MAP sensor line blew off) and it pulled only 11 inches of vacuum, so I wanted to check for any damage. I had initially suspected a blown seal (I never bothered compression testing it, I probably should have though). Besides the fact that I can't find a corner seal plug (I guess I could have just lost it while disassembling the motor), everything checks out ok visually including all apex seals. I still have to take some measurements, but most likely I am just going to replace the soft seals and put it back together.

But now I'm wondering, should I get somebody to bridgeport it while it's out? It already has what was described to me by the previous owner as a big street port, and it seems big compared to some pics I have seen of other street ports. I have attached a pic of the ports on my front iron and my middle iron.

I don't have the money to upgrade to a bigger turbo, so that's out, even though at some point I might want to. I'm not going to a 4" exhaust, that's out. I'll have to raise the idle to like 1200 with more idle timing, no big deal. With that Racing Beat exhaust, how much louder will it be? Will it drone on the highway? On my previous setup I idled at 850 and lots of other Rx-7 owners were suprised how quiet it is (until the wastegate opens to atmosphere).

Tuning is not an issue whatsoever as I do it all myself and I'm up for the challenge. I know the gas mileage will be irritating (10mpg or so? I drive 90-100% city in this car). So tell me, will bridging it really help spool my turbo noticeably compared to my current setup? Could I hit 20psi by 4000rpm even with that log manifold? And who could I send it to to get it bridged? Bruce Turrentine is 30 minutes from me, but I'm not sure if he'll bother. I don't want to attempt it myself. I wouldn't want to spend more than $300-400 for somebody to port it, but I have no idea what a fair price is.

Any thoughts on this? I mean this is a street car in the sense that it is full interior, but I've got a 55 gallon drum of race gas at my place and the car never sees pump fuel (although it will during break-in). Engine life is not a big priority, as 10k miles is plenty enough for me. And from what I've read about half bridge ports, I'd rather stick with a street port or go all out on the full bridge.

The bottom line question is: keeping my current setup essentially the same, will a bridgeport just result in more noise and less gas mileage with hardly any performance benefit unless I drop the loot on a T04R/GT40 type turbo?

 

1: It absolutley spools the turbo faster.

2: It's louder, but noise tolerance is entirely subjective.

3: A $400 FULL bridge would be at the lower end of pricing in my mind.

4: Your benefits (power wise) are still limited largely by the turbo. BP or not, the T04-S can only pump so much air.

EDIT: I've run stock, street and 1/2 bridges.........................and right now I'm building a VERY mild street port engine. I've just found there were many other ways to improve response and ultimately power output without the "drawbacks" (I quote that because I don't consider all of them negatives) of major porting. Example, goign to a divided stainless mani over my greddy log gained approx. 750+RPM better spool with slightly lower (and more equal) EGT's. Feels great, and I can still idle <1000rpm.

 

It will spool faster and improve your midrange torque, peak power likely will not improve without a turbo upgrade, but at least that's a bolt on. And OMFG you cannot beat the sound of a bridgeported fc. This video is just a 1/2 bridge 13b. http://s222.photobucket.com/albums/d...hortbridge.flv

 

classicauto hit all the points I'd personally bring up. You have large street ports and bridging them would leave really thin bridges not to mention small bridge ports themselves. With the size your ports are currently and as small as the bridge cuts would be not to mention the thin bridges that will be left over, I'd just stay with the SP. Also the T04S runs out of puff on SP 15~18 psi. Your numbers are low, but that could be the type of dyno or a really conservative tune. One thing a lot of bridge port guys seem to never bring up is the horrible light load missfire. Cruising can be a pain in the *** due to the car constantly and randomly bucking under light loads / low RPM. It can be tuned out by a very experianced tuner, but I've only see a few guys able to tune it out smoothly, and even then its still will buck once a blue moon.

~Mike.............

 

Usually try to keep out of lower lower RPM, bucking can occur. After a while your driving will adjust to the bucking. You will learn to keep the RPM slightly higher while driving.

 

i almost posted something completly diff, however on the 4th re-read i noticed that you do alot of city driving, now i have no hands on full bridge experence personaly, however my opinoin fwiw would be to not bridge it if you are going to be drivine around town that much, id prob switch to a devided manifold and pick up a devided hotside for that turbo.

As for your dyno numbers, they do seem kind of low but again all depends on the dyno

now, this whole post isnt ment to feel like a sales pitch, but i do actualy have a divided manifold and a p-trim 1.0 hotside with a 3" vband connection that im trying to get rid of if you do go that route, just let me know

-Jacob

 

Good point about the porting, if you already have a big streetport than there will not be enough meat for a strong bridge which will give risk of cracking in the future. And having a bridge fail = catastrophic failure! Loss of the bridge will give corner seal failure, which in turn will give a loss of support to the side and apex seals. When apex seals fail you can usually kiss your housings goodbye. Soooooo, stick with what you have.

 

Here is what my bridge looks like

 

IMO, I would open the ports up by this I mean your s/p! The center plate port is small almost stock looking (maybe it's the pics) but why not match port it to the end plates?
Also real nice ports have some round to them on the inside corner of the port and move the top line up some for timing this is just OM.
Why I say this is because it's your DD & a good street port will give you good numbers (430 + RWHP) my man Jorge (jm85rx7) had a 60-1 with a REAL GOOD S/P & GOOD TUNE ON PUMP GAS 93 & 14psi & MADE 409 RWHP!!!
Am not saying your port job is bad at all but it needs some work IMO...

 

^That's what im talking about look at his center plate you see the round lines & also the top port line for good timing nice job sir.^

 

thanks

 

I have decided to switch to a stainless divided manifold with divided turbine housing (keeping the same turbo though) to improve response rather than go for a bridgeport, thanks for the input guys.

 

Good choice!

~Mike........

 

im wondering if im going for a 350-400hp would a full bridgeport be worth it .

 

you can do that easliy on a streetport

 

street port is good to how much hp?the turbo im planning on using is a sc60-1? in imput if im going in the right direction.

 

It's not just ONE thing it's all in YOUR setup what works for other's may not work for YOU . A good motor, tuner, turbo, EMS, fuel & ign system will get there now all you need is time & money

As far as sp their guy out there making REAL GOOD #'s 410 + RWHP it's a combo of things

 

Let me help.......

YES, you should bridgeport the motor!!!!

 

Heh, easy enough.

 

just do it...

 

LMAO@ ErnieT!!!

I agree man, but like someone mentioned previously, spool-up time will be dramatically decreased but the TO4S will retain its flow characteristics, you can't make it flow more air than its capable off and so the increase may be minimal wrt what you're trying to achieve...
Keep the current set-up and if your budget permits, try a T04R or something similar that will get you the desired power figures...imo, the bridge will help the most if, with the new compressor, lag has increased (compared to the 'old'/current set-up) and you wanna cut the spool up time down.

Just my 2 cents.

 

if ernie is telling you then DO IT!!!!!!!!!!!!!!!!!

 

her it goes again.

what would you do: small n safe bridgeport (with big fat bridge and low port overlap) or real big streetport?

i mean it's possible to make SP that breathes more than a small BP?

 

Ok guys, I appreciate the input but this thread has already been settled, see post #12.

 

FYI, as good as this bridge looked, it snapped off (the entire bridge) and took out my engine. nice safe streetport for me from now on!