guitarjunkie28

for you guys interested in compression, here's another general rule that should probably not be followed...

your apex seals, combustion chamber, *****, whatever can handle X amount of pressure. when you lower the compression, you add empty space that lowers your pressure (all other things being equal).

ok, so you can now add more air and fuel to achieve the same pressure--not as efficient, but think about horsepower as a direct function of how much air goes into the combustion chamber... more air = more power at any given pressure.


here's how you figure out combustion chamber size:
CR=(CV+SV)/CV
compression ratio= (chamber volume+swept volume)/chamber volume

ok, lets take the renesisfor example: (10:1 compression)
10=(x+654)/x
this is the stuff we haven't done since school :p

10x=x+654
9x=654
x=72.6667 cc's

alright... now let's drop that compression down to say 9:1
(bare with me, i'm gonna make a point...eventually)

9=(x+654)/x
9x=x+654
8x=654
x=81.75cc

81.75cc
-72.67cc
=9.08cc difference

ok, so how much hp can you get from 9cc displacement at X psi? you're not gonna make any more power in n/a format, because the motor can't breath any more. but in a turbo car, you're gonna fill that volume up. you can do the rest of the math...

epitrochoid

so then how does a gt35r/62-1 compare with the t618z..or an 18g to make matters simple? how about in terms of physical size?

rotarygod

To make a long story short, the T618Z is a little child. The GT35R and the 62-1 are big strong bodybuilders. If you want big power, never send a child to do a man's job. If you want little power, don't waste the big guys time. Just give it to the little people.

Lschiavo

I just got 245 WHP and 217 Tq of a mustang dyno at 8 psi . Dynojets numbers should be around 270 WHP and 240 tq, based on other dyno sheets. I am sticking to greddy.. Fast car, lots of torque, no lag. Good luck too you.. :D

zoom44

its all in the tuning

epitrochoid

we're making the paying vendors so happy

i'm going to look into the gt35r..although with the quirky fuel and management issues if all i can do is 9psi i dont know if it's worth the effort. any input?

Fanman

If it would be a massive upgrade I would think about swapping out my T618Z for another turbo, provided I could keep the rest of the Greddy kit. Is there anything that could fit where the current Greddy turbo is (very small space), run with the EManage (even with additional tuning) & produce more hp (maybe a more modern, ball bearing turbo). I would be willing to drop the $800-$1000 for a new turbo, but it would have to work with the rest of the Greddy parts. Turbonetics is about a half hour away from me, so I would probably look at them.

epitrochoid

i'm looking for a similar greddy+ setup

Moostafa29

Yes, please report back if when you talk to them.

Jay S.

I was thinking along these same lines fanman, this would be optimal. I was thinking of trying to get my hands on a 20g from one of greddy's other kits(maybe from a 240sx or something) and seeing how it fits. I have heard that people make good power in rx-7's with 20g's. The other possible route is that if you want to use a newer ball bearing turbo Is to try and get someone to make an adapter for the greddy manifold allowing us to bolt a ball bearing t3/t4 or something along those lines in. This would probably still be cheaper than bying one of these other high price kits, and it would also be easier on the wallet because the cost would be spread out over some time.

army_rx8

why on the dyno plot do your RPM's only go up to 7100....and 7200? i'm wondering why you didn't redline it ....or at least go to 8500 (our make power in N/A form?)

crossbow

Its because the power dropped off after 7200...so they didn't feel the need to beat the crap outta the car just for a nicer looking sheet. Dyno's put alot of stress on vehicles due to the lack of airflow over the car. The big dyno fan helps, but its still not a walk in the part for the vehicle to sit there and redline over and over and over and over again.

Lschiavo

HP line dropped after that, so there is no point in running the **** out of the engine. I lifted.

Lschiavo

Thinking smart!

However, let me make people happy! :D

colin204

The largest turbo that will fit is a GT30. In doing this you will have to alter the engine mount to get a 3" inlet pipe through there.

Richard Paul

iTrader: (5)

Time to clear a few things up. Luis, your HP readings mean nothing compared to some others. First of all they say the Mustang dyno reads less. That should not be, a foot pound is the same for everyone. When they calibrate the dyno they still all use the same pound. Next you can't run a turbo at elevation and then add the correction factor. Get the numbers uncorrected from the shop, then add in for temp and RH. Not for amb pressure.

Never the less you seem to be doing well by the seat of the pants. I just came back from driving Fanmans car. I feel it was well worth the money for a kit that is intended for a street car. This is not a race kit, as such it was very nice to use the mid range torque. Sure it fell off at the top but it was not designed for that anyway. It just made a better every day driver.

I wanted it to make power all the way up too, but realized it wasn't intended for that. We all want to keep our foot in it and me too. Just buy this kit knowing what it is, a street kit. It's not built for drag racing or Bonniville. Drive it back and forth to work and enjoy it. If you intend to continue power adding to your car this might not be for you. I'd like to say bad things about it as they are in my market but for what it is intended for it is just fine.

All I can say in my defense is that it is limited to what it was designed for. Your wasting your time if you want to keep adding more power to this kit. Optimize it and that is it, live with it.

Fanman

Damnit and here I was thinking about hitting the salt flats next week ! :D Ha, ha. Good to meet you in person today Richard. Once I drop my boost controller in we'll hop in for another ride.

adrian-1

No, mustang dynos do typically read less than dynojets. This is due to them being a "loading dyno" and using eddie currents and other differences.

I dynotuned mine (greddy turbo) on a mustang dyno and ended up with 194hp/164tq. Worried about the low numbers, I took it to a dynojet the next week without changing anything and got 218hp/180tq. +25hp/ +15tp ,
Dynos are not all the same.

Post here with dyno plots. Full thread here.

rotarygod

Mustang dynos do indeed read lower than dynojets. I agree that they should be the same but it just goes to show that dyno numbers aren't everything and can't always be used to establish a baseline. The only thing that matters is how a car performs on the street or on the track. How it does on a computer screen or on paper is irrelevant.

guitarjunkie28

i describe the 62 and 35r as cute little street turbos for your grocery getter

JanSolo

I figured that a load bearing dyno read differently depending on load, ramp rate, calibration etc.

StealthFox

more like 25k plus. a good FC 20b swap is about 20

StealthFox

so basically you're saying that low compression with the RENESIS is not going to be very easily achieved, and i have a feeling mazda isn't going to be making a renesis with lower compression, therefore the RENESIS will really never see high boost then, right?

rotarygod

We can still use high compression. You just run less timing advance. Low compression allows you to run more timing advance for the same amount of boost. Up to a point the lower compression is still making less power than the high compression is at lower timing advance. There is a point in the power level where this will reverse itself but it's pretty high up there. It's not that big of a deal. Just use the high compression.

Richard Paul

iTrader: (5)

Hmmmm, The timing thing only works in a narrow range by lowering cyld pressure. It is doing so by ot burning all the mixture, therefore giving up some efficenicy.
Here's the way it works. The peak cyld pressure is limited by the fuel, you can't go any higher without getting into abnormal combustion. So since we can't exceed this number we spread it out and increase the BMEP. (Brake mean effective pressure) I like to say it's like a pyramid vs a mountain. They both have the same elevation but the mountain has a lot more mass.

We do this by taking in more mass and lowering the mechanical compression. Therefore we have the same peak but it burns at a higher pressure throughout the cycle. In a piston engine we have the valve timing to play with to also adjust the pressures. With this ehgine we don't even have overlap to reduce pressures. There is going to be a lot to learn here.

One thing I can tell you is that without the ability to mechanicly adjust the pressure boost will have a limit. With 10 to 1 that limit is going to be low.
Now you can richin it up retard the spark and inject water/alcohol. These are tools that will work to an extent, they really are band aids to a perfect running engine.

We are locked into the comp ratio and overlap so those are the only tools we have. From what I see so far getting into 10 psi is tricky. I know there have been stories of more but I think those are stories.

I have been talking in psi but there will aways be differences due to heat. I have discussed this elsware. RotaryGod has also, so we will leave that out.

This is my first ever rotary engine and I still have a lot to learn, but you can't change the basic rules of thermodynamics.

1) You cannot win

2) You cannot break even

3) you cannot not play

These rules may not apply when using thermo nuke devices.

I'll know alot more once we start the install and tune of my car. Which BTW still has not been fixed. From what has been going on with the turbos we can see that this engine is not bullet proof. I have no intention of building kits that run on the edge of engine damage. The supercharger will have an advantage of not being effected by the exhaust flow. Mine in particular will have the advantage of being a draw through. Also we intend to use aux nozzles that are controlled by a stand alone.

There are things about these engines that are specific. The large surface area is one. What the hell is all this about Fred running the trailing plug first?? What is that all about? He must know something others don't. That's fine, we don't know if it applies to the Ren anyway. RG's theory of reverse SC would work real well for me so keep up the work Fred.

Gotta go now, more to say but **** is happening.


Edit) Sorry, I just realized what thread this was. Didn't mean to hyjack it. :o