Let's talk boosted M42's

[wazzu70]

lol okay backpressure ratio? im not sure if thats really relevant and No i dont know it. Im not a master at tuning principles and to make it clear I did not tune my own engine. IAT's are in the low to mid 80s driving. the dyno however was a different story. What does spark have to do with it? Yes its fully adjustable with Ms but the stock cams are the constant. The stock intake on an m42 is something that is limiting also. If you really want to be anal you could say that the whole m42 head is also limiting, and technically youd be right. I have this feeling that you might tell me to retard my timing for more power... or something along these lines. :tsk: :tsk: :tsk:

im still interested as to what you think is limiting me if its not the cams. As far as im concerned a 300hp m42 is not limited. This was the goal for my build.

built m42 8.5:1
ported and polished head
gt2871rs @ 19psi
1000cc injectors
Full pnp MS
255lph fuel delivery

thats pretty much all info needed for this discussion.

Fist off, I didn't mean to insult your setup or anything so sorry if you took it that way. I think its one of the nicer M42 turbo setups around. I'm just trying to help you improve it!

The backpressure ratio is important to make sure your turbine is not choking out. You want to make sure the pressure in the collector is less than the pressure in the intake. If its not, then your turbine is the restriction. Since the GT28 is a smaller turbine, I figured this may be the case around that power level.

What do you mean the dyno was a different story regarding IATs?

The spark map is essential to getting decent power. Instead of telling you the spark map needs to be retarded, I was actually thinking its possibly too soft. Most people run "safe" timing maps which really aren't any safer and just leave a ton of power on the table!

When you say limited, do you mean you keep adding boost without seeing a gain? I guess we need to define what you mean by limited to get an understanding. All that stuff is a restriction at some point, but it seems pretty unreasonable to be this point.

Is the 300hp wheel or crank? Big difference, but either one is a respectable number for sure. Thats got to be a fun car!

[MF DOOM]

Dyno charts?

[Dj Buttchug]

How do you figure that?

Whats your backpressure ratio? IATs? Who made your spark map?

Sorry, I dont know the details of your build off the top of my head. I would be very very surprised if your cams were actually the limiting factor. Even though I would be incredibly surprised, if you have the data to back it up I could become a believer :)

Edit: thats not to say you cannot benefit from cams, its just that cams rarely hold anyone back in FI even if its not the most efficient route.

lol okay backpressure ratio? im not sure if thats really relevant and No i dont know it. Im not a master at tuning principles and to make it clear I did not tune my own engine. IAT's are in the low to mid 80s driving. the dyno however was a different story. What does spark have to do with it? Yes its fully adjustable with Ms but the stock cams are the constant. The stock intake on an m42 is something that is limiting also. If you really want to be anal you could say that the whole m42 head is also limiting, and technically youd be right. I have this feeling that you might tell me to retard my timing for more power... or something along these lines. :tsk: :tsk: :tsk:

im still interested as to what you think is limiting me if its not the cams. As far as im concerned a 300hp m42 is not limited. This was the goal for my build.

built m42 8.5:1
ported and polished head
gt2871rs @ 19psi
1000cc injectors
Full pnp MS
255lph fuel delivery

thats pretty much all info needed for this discussion.

[MF DOOM]

stock rods have been proven up to 300whp/tq

I believe the hardware was all arp though.

You may want to talk a tuner about the e85. Id probably run 15-16 psi if youre worried about reliability. Then again i dont know much about the stuff

[wazzu70]

That's really what I thought. I'll consider it, see if it's worth it. Put it this way, if 10psi is reliable on a stock engine running 91 octane gasoline, what boost should one be looking at to run e85 with the same reliability?

It all depends on the turbo you are using. You can't really target a pressure and compare everything equal.

What you really need to be concerned about is toruqe on the bottom end. Just because the fuel can handle the cylinder pressure does not keep the rods inside the block :)

[Vivek]

you are expecting WAY too much of e85.

i suggest not thinking of it as a "power adder" at all; rather, a less-detonation-prone fuel that's going to give you a little (emphasis: LITTLE) extra margin for error.

That's really what I thought. I'll consider it, see if it's worth it. Put it this way, if 10psi is reliable on a stock engine running 91 octane gasoline, what boost should one be looking at to run e85 with the same reliability?

[decay]

What do you guys know about e85? Is it as simple as a retune with twice as much boost, tons more power, and a similar strain on the motor (10psi on regular gas, 20 on e85)?

you are expecting WAY too much of e85.

i suggest not thinking of it as a "power adder" at all; rather, a less-detonation-prone fuel that's going to give you a little (emphasis: LITTLE) extra margin for error.

[wazzu70]

Not quite. You need a fuel system capable of flowing considerably more than with gasoline. E85 takes a lot more volume of fuel to get a stoich burn than gasoline.

E85 has a lot of advantages though, its a much cooler burning fuel and it has a very high octane.

You just need to build your fuel system to be ethanol compatible and flow enough volume.

[Vivek]

What do you guys know about e85? Is it as simple as a retune with twice as much boost, tons more power, and a similar strain on the motor (10psi on regular gas, 20 on e85)?

[wazzu70]

How do you figure that?

Whats your backpressure ratio? IATs? Who made your spark map?

Sorry, I dont know the details of your build off the top of my head. I would be very very surprised if your cams were actually the limiting factor. Even though I would be incredibly surprised, if you have the data to back it up I could become a believer :)

Edit: thats not to say you cannot benefit from cams, its just that cams rarely hold anyone back in FI even if its not the most efficient route.

[Dj Buttchug]

What is your power level? I dont see any way the stock cams are your limiting factor unless you are pushing major power. Im sure the issue is elsewhere in your system.

where in the system then?

The cams are limiting factor anywhere upwards of 300hp. You need a more agressive cam if you want to make more power.

[decay]

I just googled it, there seems to be enough around San Jose.

there is a station that has an e85 pump right near the san jose city courthouse (1st & Younger); filled up there as a "cleaner" tank when i started driving my car again. price was about the same as 89 at the time; the ethanol pump is owned by a different company so it fluctuates.

[wazzu70]

this is true. ask me how i know

What is your power level? I dont see any way the stock cams are your limiting factor unless you are pushing major power. Im sure the issue is elsewhere in your system.

[jntar]

E85 is a decent option if you have access. In my state we only have 3 stations with it so it's pointless for me. A good substitute is meth/water injection.

[Vivek]

Definitely something ill look into. If anyone else knows, feel free to add. I'd like to make this thread less about me personally and more of a resource for anyone who's interested :)