how to do 25psi on 91 octane?

[acannell]

90 daytona es 2.5 turbo

i live in california, weve got 91 octane

i want to run 25 psi

i have a giant intercooler and all the required fuel, computer, and turbo modifications

i dont want to do water or methanol

what can i do to work with 91 octane?

from what ive been reading it looks like:

retard the timing (how much? why?)

add a head gasket shim (how thick? why? compression ratio right?)

[The Pope]

run stock timing
run a G head casting
get a MSD 3 bar, FWD stage 5 and +40 injectors
MP head gasket or the MLS Cometic FWD has, at leastMP bolts, I would get ARP studs.

buy a wideband and a AFPR and run the cal at 12:1 AF at WOT

The g casting and a real cal will work together to make the engine right. Have Cindy set up the stage 5 to run 25 on the computer, if it pings the computer can pull timing and boost. Should be a nice safe combo, don't drown the engine in fuel. The g casting and 3 bar computer can handle the octain. The key is not running a boost controller. The computer must be able to do its job.

[acannell]

ooh a grocery list!

everything you listed was part of my plan except the MSD.

AND THE 12.1 AFR!!!!

Why is there so much difference of opinion on here about AFR? People have been telling me from 10.5 to 11.4 absolute max, with destruction at 12.4.

[The Pope]

Quote:

Originally Posted by acannell ooh a grocery list! everything you listed was part of my plan except the MSD. AND THE 12.1 AFR!!!! Why is there so much difference of opinion on here about AFR? People have been telling me from 10.5 to 11.4 absolute max, with destruction at 12.4.

You watch the AMS video of a SRT 4 making over 700 WHP and it runs the low 12s the whole way up. Max power is at 13.2:1 and a guy here is running 13.2:1 at 21 PSI with an SRT 4 without detonation. All goes back to the old days of Gus and Gary. Running a 2 bar cal that doesn't meter fuel or spark at high boost. So they would just drown the engine with fuel and turn the boost up as high as they could. With nearly the same engine Gus ran over 30 PSI like Terry does in the minis. They both ran +40 injectors and gus had a rise rate gain regulator to add a fuel curve. Terry only runs fuel from the +40s, Gus ran +40s and 3 extra injectors. Drowning the engine with fuel Gus's van ran around 10 MPH slower. Ask anyone with a wideband or that have run there car on a dyno, your doing nothing but destroying power under 12:1. You drop clear to 10:1 and you better be putting E85 in the thing. 3 bars can control timing and fuel above 15 PSI of boost. There is no reason to drown your engine with fuel killing the power anymore, do you still kill your food with a club too?

I like the MSD 3 bar, the GM unit is a POS.

The engine makes a lot of noise at high boost, but a 3 bar cal should have a changed knock voltage for high boost. If you watch knock with a 2 bar cal it looks like your detonating. GLHNSLHT2 faught that one for a while lol. Knock at 30 PSI is really loud compared to 10 PSI and the engine is louder just making power. Even pig rich the detonation sensor can still be going off at high boost, your just making less power. So it all comes back to not being in the stone age anymore with the computers. Hopefully I won't see anymore 15 second Daytonas this year with 25 PSI of boost

[The Pope]

to add it is really nice to run 13:1 AF to 15 PSI and ramp down to 12:1 for ragging spool up. BFMIC

[TurboTurismo]

Why is it better for the cal'd smec to not use a Boost controller and use the factory Soleniod Rob.

[The Pope]

Quote:

Originally Posted by TurboTurismo Why is it better for the cal'd smec to not use a Boost controller and use the factory Soleniod Rob.

Because 99% of every turbo car blown up here has been blown up by a boost controller. The new cals are made for a fast spool up without a boost controller. My MBC on my wagon with a T2 spools slower than a stock masi TC T2 with a stage 3 cal hooked to the solenoid. The wagon even has 3" exhaust.

Not just high boost, but boost spikes also detonate your engine. My GLHS with a 16 PSI set MBC ran fine. But twice it spiked and twice it blew up the engine. Today you can get a real compter that doesn't need the MBC. So why run something unsafe? If your racing, running race gas. You have lots of experiance running and building turbo cars. Most don't, they buy a turbo car and crank the boost with out knowing what there doing. They make a ton of power, get horrid gas mileage and blow up there engine. The new computers will give a lot better mileage with lower part throttle boost, a MBC is max boost at part throttle just cruizing which chews fuel. Want 20 PSI of boost? Buy a computer set to run 20 PSI. If your girl friend jumps in the car and puts cheap gas in when your not looking. The cal will freak and pull timing and the boost back saving the engine. MBC? Well you jump in and floor it later not knowing and the pistons melt before you pull your foot off the gas.

When you spend a page writing pros and cons between the 2, a MBC comes up really short fast. The only ones using them should be people so knowledgable that they never even ask questions here. In the past you couldn't buy a computer that really worked. People were bleeding there maps and using MBCs all the time, and O the carnage. They used to say hook up a narrowband AF gauge and peg the thing rich and turn up the boost. If the thing goes at all leaner than full rich add extra injectors. Those days should be over. Lastly there would be 10 times more TDs on the road today if no body ever used a MBC. Many just blow the engine and scrap the car, they even blame the car for melting the pistons and not there judgement. I think I could write a book on this so I'll cutter short lol

[1966 dart wagon]

Thanks for clearing that up for me, after reading that it seems dumb to even think of running a mbc with a modded computer. Thanks for the tips

Quote:

Originally Posted by The Pope Because 99% of every turbo car blown up here has been blown up by a boost controller. The new cals are made for a fast spool up without a boost controller. My MBC on my wagon with a T2 spools slower than a stock masi TC T2 with a stage 3 cal hooked to the solenoid. The wagon even has 3" exhaust. Not just high boost, but boost spikes also detonate your engine. My GLHS with a 16 PSI set MBC ran fine. But twice it spiked and twice it blew up the engine. Today you can get a real compter that doesn't need the MBC. So why run something unsafe? If your racing, running race gas. You have lots of experiance running and building turbo cars. Most don't, they buy a turbo car and crank the boost with out knowing what there doing. They make a ton of power, get horrid gas mileage and blow up there engine. The new computers will give a lot better mileage with lower part throttle boost, a MBC is max boost at part throttle just cruizing which chews fuel. Want 20 PSI of boost? Buy a computer set to run 20 PSI. If your girl friend jumps in the car and puts cheap gas in when your not looking. The cal will freak and pull timing and the boost back saving the engine. MBC? Well you jump in and floor it later not knowing and the pistons melt before you pull your foot off the gas. When you spend a page writing pros and cons between the 2, a MBC comes up really short fast. The only ones using them should be people so knowledgable that they never even ask questions here. In the past you couldn't buy a computer that really worked. People were bleeding there maps and using MBCs all the time, and O the carnage. They used to say hook up a narrowband AF gauge and peg the thing rich and turn up the boost. If the thing goes at all leaner than full rich add extra injectors. Those days should be over. Lastly there would be 10 times more TDs on the road today if no body ever used a MBC. Many just blow the engine and scrap the car, they even blame the car for melting the pistons and not there judgement. I think I could write a book on this so I'll cutter short lol

[The Pope]

Quote:

Originally Posted by 1966 dart wagon Thanks for clearing that up for me, after reading that it seems dumb to even think of running a mbc with a modded computer. Thanks for the tips

I'll give you an example. Race fuel is a great quality gas, pump is crap. When you buy Trick they tell you not to leave the can open or the fuel goes bad in 2 weeks. How long does it take for pump to go bad? I ran my computer hooked up last time the GLHS was running and one day after filling it up I notice a lack of power. Well the boost gauge said 10, not 13 that it should be at. Went to Schucks and got octain booster and a little gas from a different station. Soon the boost and power came back. crap fuel was detonating the engine. Did it matter? No it just caused me some time to up the octain and no problem. If I was running a MBC? Melted pistons.

At the track? I go out with super low fuel levels, then fill up with 111 trick. Drive the car around a bit and go to the water hole. soak the IC in cold water and go up and get in line. Plug in the boost controller and run 16 PSI. MBC spike so I can't run more than that. Get done racing and hook the computer back up and go home.

MBC vs a stage 2 on the street? 16 MPG with a MBC and 28 MPG with the computer hooked up. 7 PSI is more than enough to go fast around town and I don't chew fuel at 16 PSI at part throttle.

Today you can run a 18 PSI computer with 10 part throttle, or even ask for it to be set for 22 PSI and 7 PSI part. Doesn't matter when it comes to boost. Bolted in a stage 3 FWD computer in place of the stock one in a TC. gas mileage went from 34-32 MPG, raging power increase though and the cruize works better. You can have boost clear to 29 PSI if your can and fuel can handle it on the computer today, WTF. Why would you want to worry for one second about detonation?

Stock computers limit spool up, in timing and boost curve. FWD computers and some MP computers don't. A FWD computer feels like a MBC. Power delivery with todays aftermarket computers is night and day better, much of what you want in a MBC for driving is built into new cals. Expensive? Most are under $200, I've bought early ones for $100. Sure you can buy another junk yard engine for $100, whos got the time to change it?

So save the MBC for a little track abuse with expensive quality fuel, but plug the computer back in on the street

[acannell]

where were you three months ago when i was building this engine???????

[The Pope]

Quote:

Originally Posted by acannell where were you three months ago when i was building this engine???????

If I lived in socal like you I would bolt on everything I was going to use on the engine and drive the car down to Cindy in Texas and get the thing done perfect. They can build the cal to run your car perfect at 25 PSI on the dyno, which is the best way to go. I would talk to them about a high low switch, 18 PSI max and a 25 PSI max. No MBC for the track then either. I have 2 trim cals, 4 different settings for boost and others for fuel and spark control The trim cal is a toy once adjusted, I know but there sweet.

[TurboTurismo]

WOW, Good write up Rob..... Thanks...

[beejie21]

Dang... now I feel dumb for even THINKING about a MBC for my car. Haha my motor thanks you for saving it's life.

[Ondonti]

13.2:1 is NOT the best for turbocharged horsepower..let alone n/a horsepower. That is just wrong.Low/mid 12's depending on your engine. Every engine is different, therefore there is no concrete rule.

Also, giving advice for people running 91 octane that is based on an AMS car that is running 100% C16 racing gas is a very bad idea.


1 bad batch of gas and say goodbye to your motor. Its pure luck if you survive bad gas and you were running irresponsible setups.

[speeduphoria]

Quote:

Originally Posted by Ondonti Also, giving advice for people running 91 octane that is based on an AMS car that is running 100% C16 racing gas is a very bad idea.

Also personally I think the AMS car dyno was skewed.

Like Ondonti said every car is different, 12.5A/F with high boost on race gas is Ok, or low boost pump gas(15psi max).


Pope if the computer controlled boost works so well then why are you changing it to a MBC at the track??