1wide7

iTrader: (1)

why do most rx7 only boost to 15 on pump gas while other cars are fine upto 20+psi with out anything fancy like water injection??

example new evos are right around 19-20 out of the box!
and theres a few people around me with other cars running 20 psi on pump with no problems?

1wide7

iTrader: (1)

nobody know ???

Maxthe7man

I dunno, I run 20 psi on pump gas...

usmcjsy

iTrader: (1)

I am not sure, I used to run 20psi on the stock FC turbo with pump and had no problems. What size is the EVO turbo..? Once you start upgrading to the bigger turbos you will really need to limit the boost to around 15. If you run 92-93 octane on the stock turbo at 20psi you should be fine if you have the correct mods to do so. As far as people saying the turbo really makes no more gains after 12psi or whatever I could tell a good differance between 12 and 20psi on the stocker. Others say you will ruin the turbo running that high of boost on the stocker I did not have that happen either. Anyway if your getting knock just retard the timing a few degrees. Also maybe look at getting at least one of the Rtek upgrades that retards the timing for you. If you are looking at a hybrid or a full turbo upgrade yes 15psi will prolly be about max on pump. Thats true even for other cars with big turbos. Some people may be running a mix of pump and race gas with bigger turbos at 20psi, or they could flat out be lying. Or they are just a real gifted tuner. Either way there comes a point where the race gas will have to come into play. I just run the BNR stage 3 at 15psi on pump. I am happy with the power and to me running street tires and pump gas makes it a true street car. Others think a true street car is just haning a plate on it and running C116 and slicks with gutted interior. To each his own. I dont have all the answers just letting you know what I have personally experienced and seen.
Jeremy

Chris Ng

TD07-25g, 18psi, 91 octane
12 degrees max advance by 18psi
Havn't blown up yet...

Maxthe7man

My Mom just tells me I'm special....

Hey and this time its with a motor that wasnt blown before it was installed....

jacobcartmill

iTrader: (6)

it really depends what compression rotors (or pistons in the case of the evo 4g63's) you're using...
i have read many places not to go over 16psi on pumpgas (93) with 9.0:1 rotors and not to go over 18psi with 8.5:1 rotors

Marshall

They have knock sensors that actually do something.

Maxthe7man

Hmm... Who ever wrote that was wrong......

Deusxmachina

Testicular fortitude?

It wasn't all that many years ago that certain imports weren't often found running more than 18 or so on pump gas simply because few people wanted to risk blowing up their cars. Then more people kept trying it and not blowing things up, (unless they half-assed it), and now it's getting fairly common for guys with big turbos to be doing 25psi on pump.

I think most turbo Buick guys are still the same way. For years I'd read the forums and see people cranking the boost to the moon on race gas, but on pump most would only run 15psi.

fastcarfreak

Because our cars a suseptable to even the smallest amount of detonation, and most piston motors can actually handle a little bit of detonation. Like marshall said, our knock sensors are crap on our cars. You can run 20 psi on pump gas, but its just not safe.

You also dont need to run that much boost on an rx7 to get it to go as fast. Most of our turbo setups are worth about 350-420 rwhp at 15 psi. Try getting that much power on an evo at only 15 psi. My buddy runs 26 psi in order to get 342 awhp on his evo (stock turbo), my other buddy has a huge upgraded turbo on his evo and runs 35 psi on race gas, and makes 500 awhp. If we were to run 35 psi on our car with race gas, we get like 600 plus rwhp.

radkins

I run 20psi every day on pump with water injection. Probably putting down 450ish.

jacobcartmill

iTrader: (6)

whats right then?

Maxthe7man

The safe limits with high octane pump gas (91-94)(r+n/2) that has been proven to me and used by me are 20 psi with 9:1 rotors and 25 with 8.5:1, past that point at reasonable air fuels it will detonate irregardless of what you do with timing/plugs/rotor cooling etc etc..If you drench the motor in fuel just to run some crazy boost pressure, chances are you could make more power with more efficiency at lower boost levels .. Those numbers are what generally tunable on pump gas given everything else is in order..Max

88fc3sw/HX83

Max, I agree with you about the "25psi with 8.5:1 rotors" theory because I've run about 22psi on 92 pump (on accident due to a faulty boost gauge and std wastegate) and the ONLY thing that broke were the rear and front plates! At that time I was running the S4 motor which have less material around the pins

Jim

books

iTrader: (8)

I would like to run more than 15psi. Would you provide some more details on how this has been proven to you?

RICE RACING

I've been doing this for 6 or 7 years now?

First car was on WI then owner took it off, he runs B10EGV plugs, 12deg timing 8 deg split, 10.5 to 10.8:1 AFR at WOT and mid to high revs runs 20 psi all day every day.

On my own car I ran up to 23psi on 13.7:1 AFR with WI though again for a long time, B11EGV plugs.

Another ******* running 25psi 9.0:1 rotors B10EGV plugs, 12 deg advance 8 deg split, WI, 9.0:1 rotors.... running for a long long time, no problems what so ever. 11.7:1 AFR with WI (very very safe tune).

WI or without you can run 20psi safely in my experience on T04 frame sized turbochargers and using air to air IC on either 9.0:1 or 8.5:1 compression rotors on pump gasoline.

Right AFR, right timing, Engine temp under control, and you will have no problems, only issues you will face are rear tires that suddenly melt each time you get on the gas and a very quick loss of drivers licence

books

iTrader: (8)

"First car was on WI then owner took it off, he runs B10EGV plugs, 12deg timing 8 deg split, 10.5 to 10.8:1 AFR at WOT and mid to high revs runs 20 psi all day every day."

Is that 12 degrees at peak torque, 12 across the board, or 12 at max rpms?

Maxthe7man

Books, I dont know how advanced you are in tuning, so I might be posting the obvious to you in this..Without posting an entire timing map, its hard to say, and if you start building a map from a blurp, its not gonna work as well as the map the blurp is from..
Its more than just a given timing number at a give boost at a given rpm, to take 12 deg and build a map from that, even though it worked for that guy , it might not work for you. Depending on where you hit boost, where in the map it runs through on boost and how you drive car is how you derive a timing map that will work...
Ok, so you know 12 deg at 6500 will work at 20 psi, what about at 12 psi at 3500, and as the turbo reaches 20 and passes through the other cells..
Thats whats important about tuning, is making sure every cell is covered with a number you know is good for that load/rpm point...Its pretty easy to build a map with a few number in that will work, but its the one time you hit a hill and you spool earlier than usual, and you tread into a portion of the map that has never been hit or datalogged, and bad things happen.
Changing boost curves and or controllers will affect how the turbo will boost through a map.
I watched a guy tune 3 rx-7's in a row, each one to the same boost point, the guy has tuned more rotaries than you or I will ever see in a lifetime, yet he ran through each map point on every car listening for knock with a knock amp..The lesson he taught me that day,not one car is the same ever...
What Rice is giving is some guidelines to build a map around..You could go set all your timing to 12 now across the board and run 20psi but it would be far from optimal and far from tuned...And peak torque timing will depend on the port, its shape, length, and also the mass flow rate of the turbo at that psi.
There are some really good references in the Racing beat manuals on timing, you can take the n/a figures and the referenced boost figures and derive some nice timing curves from those numbers for pump gas..