Max boost with stock downpipe?

[wiggman2030]

Getting the rex mapped soon, would like 350bhp+ if possible my spec is:

Large street port,
Stock Twins,
Decat,
Kakimoto Regu 92db Exhaust,
K&N style induction kit,
Power FC,
GReddy Style FMIC,
Koyo Style Rad
Rewired Fuel pump,
Stock Injectors

As I have the stock downpipe what is a good amount of boost?

[clive]

You will find that stock twins don\'t like living with more than 1 bar boost so regardless of your down pipe, theres your boost limit to get it mapped at.

Hope this helps

[Aubec]

Gonna struggle for 350 with stock fuelling: need bigger injectors and/ or signficantly higher fuel pressure.  Stock downpipe is restrictive too.

Go to 1600 secondaries or 850 primaries, and an update pump and you might get close to 350 at a real push...

[turbotoaster]

you can go to 350bhp on stock fueling, id just advise you up your fuel pressure as it fits 100% duty at 360bhp on stock fuel pressure.

Or like Aubec says put some 850cc secondarys in your primary rail, thats what i did and at the same power i hit 75% injector duty, nice and cheap, they only cost me £30

ive got a stock downpipe as well

You can run more than 1bar but its a sliding scale, the more boost you run the less time the turbos will stay together, there are people running theres up to 20psi but your expecting at any moment for them to pop

[SiH]

At 20PSI the stock tubs will jsut be blowing superheated air - it\'s pretty much pointless.

At a 0.9bar, my relatively new 99 spec twins lasted a whole 6 months.

I\'d really advise you to fit a downpipe - te stock one is a massive bottleneck. With your mods an a downpipe I made 340ish, totally stock fuelling. 94% duty.
With a rewired pump I\'d have thought you\'ll happily make 350 at similar duty.
For the £100 or so of a downpipe, it\'s well worth it. Just don\'t get an eBay one, as they\'re invariably LHD so won\'t clear the column.

[turbotoaster]

not really SiH they will make power at 20psi but like i say, they will blow at anytime, im not advising he does it just that they can go that high.

Id say run around 15psi as thats nice and reliable, anymore than that and your going into unknown territory in terms of life.

[jackaleks]

i hit 320 at the fly with totally stock fuelling and stock twins at 0.8Bar, that\'s with 92% injector duty though so you\'ll need to do something to the fuel system. at the very least a stronger pump and a decent regulator.

[neil_jdmr]

With stock twins/fuelling you will max out the injectors before you get 350hp imo, even if by some tweaking you get 350hp then it will not be a safe and reliable tune.
 
Get a fpr and an 044 or some bigger injectors if you want 350bhp on twins and maybe buy a second spare set of twins.

[kompactor]

Rewiring the fuel pump will help get more out of the system. The stock wiring has bad voltage drops, both on the ground and the power wire side. Here\'s a very useful fuel calculator too. Shows fuel pressure, pump, and injector requirements for estimated power levels. http://www.wannaspeed.com/index.php?main_page=page&id=19&chapter=1

[SiH]

Rewiring the fuel pump will help get more out of the system. The stock wiring has bad voltage drops, both on the ground and the power wire side. Here\'s a very useful fuel calculator too. Shows fuel pressure, pump, and injector requirements for estimated power levels. http://www.wannaspeed.com/index.php?main_page=page&id=19&chapter=1

That\'s based on USBHP though - the exchange rate on them is similar to the £/$ ratio.

[kompactor]

It has both flywheel and rear wheel hp. Rwhp should be pretty universal. In any case it shouldn\'t be hard to convert.

[turbotoaster]

unfortunately not, because looking at it assumes that you believe dynojet figures which we all know are false.

For you guys over the border, imagine our power figures are the stuff you see on mustang dynos which are around 15% lower than dynojet

[kompactor]

So you take the numbers and reduce it by 15% or whatever. To make it easy just add it to the "drivetrain losses" area.

A stock 93 RX7 is rated in the US at 255 BHP. On the dyno here a healthy stock RX7 would make around 217 or so.

The calculator defaults to a stock 3rd gen RX7. So if anyone knows how much power a stock Rx7 makes on a dyno there, it can be easily adapted.

So say a stock 3rd gen RX7 makes 175 RWHP on the dyno there. Thats 30% from the rated BHP that the calculator defaults to. Under drivetrain loss enter 30% and it\'s now configured. Of course it won\'t be perfect, but it still allows you to quickly compare different setups and get an approximate limit for a given fuel system.

Another way to do it.... is to enter your current fuel setup and manipulate it until it matches your current power. (if known) Then if you\'re planning for more power you can see the ideal fuel system adjustments that may be required.

If you\'re trying to dial the calculator in using stock figures then I would use the default BFSP (0.64), as soon as you are comparing tuned RX7\'s I would change to the 0.62. This is because a stock RX7 is generally much richer then a properly tuned RX7.

[turbotoaster]

actually looking at them figures on that calculator they dont seem that bad, for example i used this

43.5psi fuel pressure
85% inj duty on stock injectors
0.62 BFSP as alot tune a little richer than the stock map on boost

that gets me 365bhp or 310whp which is pretty comparable to what a couple of fds got on reworxs dyno

the only issue i can see is that it says you can get 399bhp on 100% inj duty on stock injectors and stock fuel pressure which you cant do as far as i was aware

[kompactor]

Well you wouldn\'t want to run 100% duty. This would mean the injector is held open and would certainly cause injector failure if continued to run like this.

When I did my first single turbo setup is was a t64 on a ported engine and stock fuel system. At 10 psi I saw some peaks of 100% duty on the pfc. (quickly changed to a larger fuel system) But the setup at 10 psi made right around 350 RWHP which is pretty close to 400 flywheel.

Also if you tune richer then the stock map (not sure why you would) you would want to use a higher value BFSP. I\'m referring to the map in the stock ecu, not the base map that comes with the PFC. If I recall correctly the target AFR\'s for the factory map was in the 10\'s in many boost areas. Most of us tuners go for mid 11\'s.

Sounds like you found some values that work pretty close for you though, and .62 is what I usually use for a rotary that\'s been tuned.