I've had experiences with both SP and BP. Has anyone factored in aggressive street-porting in this equation? I've never dynoed an aggressive SP, but it feels almost the same power as my current BP...

My simple 2 cents.

 

i think people get carried away with boost doesnt equal power idea. I would disagree if you are comparing 2 different turbos on the same engine. technically, if you are still within reasonable efficiency ranges of given turbos, their flow will not differ much at the same boost level. the only difference will be the affects of temperature.

I can understand the flow will be a lot more on a bridge or streetport vs a stockport, given the same boost level, cause its flowing a lot more air

 

you misunderstand the point. The discussion that the others were having were why does this bridgeport using this turbo make less power at some psi and this streetport using this different turbo make more power at less psi?

I didn't say the turbos were different, other people said it. Of course using the same turbo, power rises as boost rises. You're going to make more power at 20 psi than with 10 psi when using the same turbo given that it's not choking at 20 psi. (Meaning the turbo can support positive flow at 20 psi, a stock turbo runs out of gas at 13-15 psi). The point is, when making comparisons with different turbos, boost is not the all-important factor. If I have one turbo that's boosting at 18 psi and moving, let's say, 1100 CFM and I have another turbo boosting at 12 psi moving 1500 CFM, which one makes more power on the dyno?

Mass flow and CFM can be used similarly, true, the most important part of the equation is the mass of air being sent into the combustion chambers. CFM is an indication of flow. Actually, I'm not quite getting the difference between mass flow and CFM now.

 

I know this has been mainly a turbo discussion, but what about streetable N/A's? Which would be more tolerable for daily driving, the agressive street-port or the half-bridge? Has anyone ever even considered semi-pp for tolerable street use?

 

I know I'll probably get flamed for this but I am gona oss it out there since we are referencing boost with no respect to what it truly means for the power equation.

The most comonly misunderstood concept is that boost = power. While this is mostly true, it is actually a side effect of running more boost. Roen got really close to the mark in one of his previous statements.

Boost does not increase power, it allows for the motor to burn more fuel to increase the expansion of the gasses inside the combustion chamber. Now obviously increasing boost will usually result in an increase of power, but to take full advantage of the raised cylinder pressure good tuning is required. But almost everyone on here knows this and is virtually useless in this discussion.

Now for what Roen said when comparing the two motors above. The comparison was made between two port styles running two different turbo's. Other than the fact that any analysis of the outcome of the dyno's is basically useless to this discussion because there are to many different factors to consider. To sum up the correlation that anyone with two functional eyes can see, Ted's car makes more power till around 3200 RPM at WOT, then the BP takes over the power delivery and absolutely smokes up top. The power curves of 3200 RPM and below show that Ted is creating more power, but it is more of an academic difference than a tangible result.

In short, it was a bad comparison and what Ted is trying to get across (I think) is the driveability and power production at light load and partial throttle is superior on a SP. Unfortunately, no one goes to the dyno to lay down a power map of 20% throttle and light load therefore this argument can only be resolved by those that have driven both a SP and a BP of some type that have similar setups and then we have to rely on their opinions of whether or not the BP is streetable or not. This is a less than ideal situation so the more input the better it gets.

Now since we have no control group or any way to gaurantee that the bridges that were cut were even remotely the same this means that the results we do get and the opinions formed are going to vary on multiple levels. You can take someone that ran a bridge that had massive overlap and very poor low end performance and they might say that they don't think a BP is streetable. But if you take this person and put them in a car that has slightly higher bridge cuts resulting in less overlap and better low end performance, they might change their mind.

All of this information obviously shows us that any scientific basis that is made out of a lot of the information in this thread is basically moot.

But again, I must digress.

The original question posed by this thread was aimed at the conclusion that a bridgeport was overated. I know that I left the title and my original question vague, but I will be honest and say that I didn't expect this thread to get anywhere near this much attention but I must admit that it has spawned some very good info.

Sorry for going on and on, but that was some stuff I wanted to get out there.

Now, I was going over some info for turbo matching and there was some good stuff over in the turbo section, but I didn't find anything on how much air a brodgeport motor can eat. Does anyone have any idea what this may be? This would be extremely helpful in formulating what turbo would be best matched to a bridgeported motor. I know many people on here have already tried mutiple combinations and have found what works and what doesn't and I would personally like to see what different people are running to see what options are out there.

Also, Roen brought about a very good question above about NA and I regret to say my lack of information on non boosted applications. My friend dabbles more in the NA motors and he told me that he fully plans on running a bridge motor in the near future, but he is a little hadcore and would probably say the same thing about a PP motor.

Again, thanks for the info.

-Maniac

 

blah
this has turned into road racers vs drag racers and there diffrent needs
including steve who retired as a drag racer and is now a road racer...............

 

So how does david feel about making that statement in the first place now?

 

Roger
I challenge you to a road race.
We both must run on slicks on the rear and skinnies on the front.
At the end of the 1/4mile who ever makes it around the turnoff back to the ticket booth first wins!
That should put an end to the BP vs Sp debate and should satisfy both parties involved, drag or road racer.

 

LoL!!!!!!!!!! hehe

 

two points... backwards =)

2. everyone with a bp, says they make more low end, but if you look at the plots ted posted thats not the case. you ever driven a stock turbo fc back to back with a gsl-se with headers?

1. the port and turbo (and fuel, and exhaust etc etc) are a means to an end. you need to decide what the end is....

 

wuss, detune it, and go road racing! they still have standing starts =)

 

I don't think he honestly cares about anything that was brought up in this thread. He has a type of ricer mentality when it comes to porting regardless of whatever information is given. He has a streetport therefore streetports are the best port there is regardless.

J9FD3S, what are you getting at with the stock TII and a GSL-SE, I'm not poking fun but I seriously don't get what you are trying to say.

 

I'm glad you mentioned this.

The dyno plots, even at 100% throttle, has implication is on engine VE.
Now, don't go asking me the esoterics on this, but there is a corrolation between WOT dyno runs and engine VE.

With most of the replies already mentioned, a lot of it was unnecessary.
We're not talking about racing - racing applications are already proven: as long as the rules allow it, port the motor however you want to.
So arguing about racing applications is a waste of time.

Sure, to the guy who questioned "streetable", it wasn't explicitly mentioned by the OP - *I* made it a point with my replies.
See above - to be arguing BP's for racing is stupid; BP's are proven in racing as long as the rules allow for it, period.
Thus, I brought up the point about being streetable...


-Ted

 

Ted, any opinions on NA's? is the lack of torque production from not having a turbo an even stronger argument for a streetport on a streetable car?

 

have you driven both? the gsl-se feels so much better than the t2, especially under 4000rpms. i remember the first time i drove a t2, i thought there was something wrong with the gas pedal.

but i think the t2 out torques the gsl-se, if you look at a dyno chart. this is the same thing the BP people are saying, it feels more responsive, but it doesnt show on the charts....

 

Ahhh, that clears up a lot of my misunderstanding for the most part. What you have said then is completely reasonable and I won't argue whatsoever.

I guess then the next question is, is it possible to cut a different type of bridge for a motor not designed to go all out power. Perhaps something with a little less overlap and some more light load tuning could be created to make a perfect daily driver that has higher VE capabilities than a normal streetport.

I think tuning has a lot to do with drivability. To many times have I seen some car built for maximum power with little regard to light throttle maps. Basically most of the tuning goes into the WOT runs and then they throw together a map that will just let the car run on the street.

This was more into what I was trying to say in the first place, I just couldn't get the wording right.

-Maniac

 

I have never had the pleasure of driving a GSL-SE but I have driven many NA FC's, a few turbo FC's, and more FD's than I can count.

Regardless, I do see what you are saying. I like the response of the NA but I like the power of the turbo more. There in lies the problem. I want to try to make a car that has fast transient boost response and does it very low in the RPM range to produce a more full and usable power curve on road courses / Auto-x / Daily driving without to many concessions to light load and low rpm power / drivability.

Basically, I am going to spend a lot of money to get my idea developed just right.

 

Sorry, I'm not qualified to make any comments on NA application, since I don't have enough experience with them.

Personally, I would never street a NA BP myself - there is just not enough justification in my book for a BP for the street. If I wanted more power out of a rotary, I'd just boost it.

Now, I didn't say you CANNOT street a BP...so hopefully everyone gets that straight.


-Ted

 

I think this is where the HBP (BP on just the secondaries) might just fit your needs.


-Ted

 

Would there be any point to streetport the primaries while putting a bridge on the secondaries?

 

hell yeah, keeping it streetable while also retaining some of that bottom end that is nice to have from time to time. Some say full bridges are streetable but I could understand how thats not for everyone.

 

That's the whole idea behind the half-bridgeport, Roen.

B

 

oh by the way brian I showed the ports to a friend of mine who is helping me with the build and he says there is no way you can be doing that by hand. He says you have to be using a machine, lol. When I told him you did it all by hand he was amazed.

 

I wouldn't go back to halves but thats me!

 

Brian is a machine. He's an android. Didn't you know that?