anyone know what a streetported 13b turbo would make carburated? horse power and torque?

 

I'd guess around 250whp on modest boost.

 

do you loose all torque? or keep some with the turbo. any idea when the turbo starts boosting?

 

Spooling depends on the turbo. You'll have PLENTY of torque with a turbo'd B



--Alex

 

carburated?

 

Your question is too vague. Everything depends on your combination.

 

As Directfreak says your question is too vague for a detailed response.

As a very rough guide, assuming you want to add a turbo to the present set-up then a 87 BT gave 180hp, add 30 for a mild streetport, deduct 5% for a carb , then you are looking at 200hp flywheel, say 160rwhp. Adjust if you go for a large turbo and boost.

Why do you need to know, just do it and dyno, then you will have an accurate figure depending on which dyno you are using, the temperature, external air pressure, etc.etc.

 

I'll make that all day long without a turbo dude.


--Alex

 

and thats using stock boost, if im building a motor it will be built to hold boost

 

I maintain.

 

specifically:

dellorto carb, decent sized street port on a s5 engine, stock s5 turbo, FM intercooled running about 15 pounds of boost


how drivable might this set up be too?

 

Sounds similar to what I'm doing. I'm hoping to get about 300-350 RWHP from 15psi boost. But I'm using a streetported S4 13B 6 port as a base, throwing S4 TII rotors and e-shaft in it and using either a Mikuni carb or a holley 650. Its sorta based on what directfreak did with his car. Rebuild will consist of all new seals (I mean ALL new seals and springs), hardened stationary gears, and standard bearings. Using the stock TII turbo might be pushing it for 15 psi boost, reliably anyway, and drivability might suffer.

As with any carb, drivability isn't the greatest among todays standards. FI is always going to be better, but it would most likely still be fine for street use.

 

My engine is a Cosmo two rotor, with stock (lower compression) rotors. You are not going to reach those numbers on an S4/S5 turbo. It's simply too small.

 

It will lean out in third gear.

 

Why will it lean out in third?

 

Um, it wont lean out at all if you have the correct fuel pump and good tuning.

You wont make any more than 250 RWHP on a s5 turbo. That's on a street port, 17 psi of boost, and it will all be at 5000 rpm, whcih is calculated to be roughly 250 ft-lbs RWTQ. Then, your boost will progressively drop off to 7psi at redline.

Your lag will be minimal. The stock turbo tends to spool well. Expect full boost by 3000-3500 RPM and spool around 1800-2000.

These numbers are for a fuel injected 13b, I would expect them to be roughly the same with carburetion. Wide Open Throttle (WOT) should be just as efficient with a carburetor as with EFI, as long as the Air Fuel Ratios (AFR) are the same (good to keep around 10.8-11.2 at WOT).

As for drivability, carburetors and turbos usually dont mix well (I know plenty of guys here are doing it, and like them, but carburetors will never be as smooth and silky as a properly tuned EFI). If you are used to a stock FB, or a fuel injected car, the carbureted turbo will run rough in comparison. You may be able to bear it, though. I suggest doing a t2 engine swap (with full harness and ecu... i have a friend who is putting haltech in his car and has a full harness and ecu off an 87 t2 if you want it).

 

"Quote:
Originally Posted by fitzwarryne
say 160rwhp.



I'll make that all day long without a turbo dude.

"

Yeah, but the torque is much less n/a'd. Anyone with a equivlant 12a or 13b turbo'd making 160hp turbo'd and a n/a making 160hp will DEFINITELY not have the same torque curves. That is one reason I like my turbo setup much more then before I had that.

 

agreed!!!

a stock s5 turbo motor with a 45 weber , 2 1/2 exhaust, non intercooled made 230 rwhp and 215 torque..
thats the lowest dynosheet...
i had a nikki that made 550 rwhp 12a bridge

 

Your robert from rotaryshack aren't you??? Well, if you are, I sent an email last night asking about using a mikuni carb with a turbo. Will it work?? I would like to know because I've been offered a mikuni of unknown size with intake manifold.

 

I had this setup pretty much

upgrade your stock turbo with a 60 compressor wheel and housing and you can make 300whp

i did 250whp@10lbs of boost non intercooled with a 60 compressor upgraded s5 turbo, stockport s5 13b, 50mm weber and ran 12 second quarter miles pretty easily on the stock 13 inch wheels.


drivability isnt as good as EFI by any means.
full boost can be achived on the setup i mentiond under 4k rpms in 1st gear.
curising the boost will raise slower but it will be very linear.
first gear is honestly a bitch unless your racing. just bump it and shift into second.

It may be differnt for others. my car was light as hell. very stripped and I have a race type suspension in my car.

 

Alex-7. The problem with throwing hp figures around is the great majority of dynoes are extremely inaccurate and useless for absolute measurement.

Remember the Mazda factory racing 12A with PP, which needed a rebuild about every 5 races, only produced 305hp flywheel, approximately 245rwhp. Some of the most accurate hp measurements of modified engines was by Paul Yaw. He was getting typically around 200hp for a street port and 240hp for a bridgeport- and this was flywheel. RWHP would be typically 25% less.

A good way to accurately test the local dyno is do a test run on a stock 12A RX-7 and the calibration figure should be 72hp. In a club dyno day for which I got sheets the stock vehicle was getting 65-75rwhp according to its condition.

Big turbo. big boosted engines can produce fantastic hp but you need mega modifications, gearbox, driveshaft and diff just to start with. A good sreet legal set-up should give you a 1/4 time of around mid ten seconds.

In simple terms the real measure of your hp is the 1/4 time. What is your best documented time?

 

i use a stock gear box and rear end by the way.

 

I will diasagree here. Too many variables for a good E.T.
For good idea on horsepower, you need the MPH at the 1/4 mile, and
the correct weight of the car. That's a much better indication of
true horsepower.

The formula is: hp = weight * (speed / 234)3

http://www.dsm.org/tools/calchp.htm

 

in regards to the mikuni with the intake manifold that's been offered to you, if you decide not to take it, i may be interested. im looking for one, but the price has to be right.. i can wait a long time to get one, just has to be cheap. let me know

nick

 

Directfreak- Your reference give the formula for both the ET and speed. I think they are both good rules of thumb. What I was getting at was the street performance was a relatively constant measure compared with the variability found in different dynoes. For example as Redhead pointed out in another thread, the make of dyno used generally in the US gives a 20% higher reading than dyno makes used elsewhere.

It takes some 500rwhp for an Australian street legal RX-7 to achieve a 10.5 second 1/4 compared with 610hp for a US RX-7. The hp mesurement is less important than the ET in measuring power.