Thinking of going semi.

Can anyone share info on the benefits. I've "heard" that HP shifts to the right so you need to rev a lot higher and will lose low end HP.

Any info at all is appreciated

Thanks,

Anthony

 

Don't do it, that ****'s gay!

 

For the street no. For racing yea.

 

My opinion, based on dyno graphs of various setups is, that there is no loss of low-end power but since VE curve is so flat even at very high rpms, it makes peak power in narrow top-end range, assuming flat boost curve. Close ratio gearbox would be needed for taking advantage of it.

On the other hand, "lesser" porting style (stock, streetport) have inferior top-end VE, but its better to have peak HP at lower rpms but carry it for 2000 rpm band. This is powerband IMO. More boost will be needed for given output obviously, but right sized turbocharger will gain efficiency at higher PR and there is no reason to fear added heat from boost if intercooling and fuel is good for given combination.

Overall, large overlap setup will be more delicate on turbo sizing, tuning and exhaust setup and less flexible in regards of gearing and driveability.

 

Dont think about it. just do it!!! im building mine semi pp half bridge for the street

 

Also building a semi/half bridge. The semi port is going to be 9/16.
Also wondering how big others are running?

 

1" id.

 

i do mine 0.82 and have done it 1''

 

After much debate on wether adding my two inexperienced cents or not, I decided to post what I had planed, and had to postponed for a couple of years...

My plan was to run semi pp on my dd car, however my plan was to have two intake manifolds and maps. For the track run the semi PP manifold and map, and for DD, swtich to the non semi PP manifold, and tune.

I guess the beauty of semi PP is that you can go from semi to non with a manifold swap, something you cant do with a bridge.

 

i see some people making custom manifolds and having flaps on the semi ports

 

I have not seen any increase in power going from a turbo charged bridge port to a turbocharged semi.

But what i have seen is longer lasting apex seals. The reason for this is is the fuel "in our case we use methanol so it even helps more" acts as a coolant for the apex seal everytime it passes over the semi it picks up a nice drink of methanol.

Those that have made 900rwhp will start to notice that even on methanol the cumbustion will cut right through a apex seal without running lean.

Hope this helps.

 

Thanks for sharing this info Dee.

Mine has a 1" diameter.

 

Did we just went back in time when the pros used to post good info on this forum?

You sir are the man

 

Do it Ant! Even if you don't rev it higher, your torque jumps as well and is very broad across the board.

 

Ernie, how bad was your idle with the semi PP?

 

I had a street port/semi and it was barely noticeable

 

just do it if u dont like u could always do something different

 

go for it you'll never regret it!

 

For a long long time i ran just a big streetport. The best e/t i ran with the streetport is still my PB of 7.17.
Last year we changed to a semi pp. We have been chasing 'issues' with the car and as yet we haven't run any quicker with the semi BUT it's making at least the same power with less boost.
We have not lost any bottom end power and i don't have to rev the engine any harder than i used to(11k).
My PB 60 ft time is a 1.010 and this was with the semi pp launching at the same 2 step rpms as with the streetport(8800RPM).
Hope this helps

 

Thanks for all the advice on this, I picked up a spare shortblock and going to make that one the semi and leave the streetport in the car running for now.

Anthony

 

do it Ant.. soon my kid will be testing this one here in her street car..

 

Nice! I'm curious to see how a semi idles too, let us know.

Thanks Ito

 

should idle just like a bridge or peripheral port since it has the overlap.i'm getting ready to install a semi in a first gen in a couple of days.

 

i know this threat is old but i searched but couldn't find anything else about semi pport.
i want to ask if anybody know (try,have any experience) with the combination of semi pport and semi bridge port

 

There is no point to even do that honestly its either half bridge or semi, i personally choice semi cause i dont like the cutting into the plates just run a semi with a street port