AngryTaco wrote:What pistons are you running Cricket? I was looking at getting a set of wiseco and bump the compression up to 10.5:1
You're asking for even more detonation problems than you're already having by going 10.5:1 with boost. You could get away with doing it on a decently cammed 4v/cyl VAG motor running E85, but not something as detonation prone as the 20vt.
Audi sport used compression ratios even lower than the MC1 in the early 20vt group B cars. If you're going to model after something using ancient technology like CIS, just make sure you use an example that had a well-funded engineering department and factory backing
E85 is definitely the key to success for the 20vt. Audi sport 10 were in the 6 to 1 range and guys like Jim Green ran with stacked gaskets on mc1 engines for around 6 to 1 ad well.
Hank wrote:E85 is definitely the key to success for the 20vt. Audi sport 10 were in the 6 to 1 range and guys like Jim Green ran with stacked gaskets on mc1 engines for around 6 to 1 ad well.
Hank
HOLY SHIT! thats crazy low. Im not looking to go huge power out of my MC1, so I think I should be OK.
"If you can't find one, make one"
Dallastown, PA
1991 Audi 80 quattro (20vt project)
1991 Audi Coupe Quattro (project: my first 20v)
2007 Mitsubishi Raider(Dakota in disguise)
2019 Chevy Cruze RS hatch (wife's little red sporty car)
I couldnt imagine the off-boost torque with that low of a compression. It's given me something to think about. I'm pulling the head off tomorrow and inspecting the damage so that may determine what happens in the next few months.
1986 4000cs Turbo Quattro
2001 Dodge Dakota R/T Standard Cab
1990 V8 quattro
1995 urS6
-Hersh Performance and Racing Products-
Most orders are being refused until further notice. Please PM
If Audi Sport did it I'd trust it to be a good idea. Run a LWFW and 4.11's and the off boost won't be quite as bad. Spool it with some a quick spool valve, nitrous and throw some meth at it just for good measure.
-Phil
87 5ktq - 20vt
91 v8 5spd - Why?
05 S4 - Gone and very much so forgotten
14 TDI Touareg
AngryTaco wrote:I couldnt imagine the off-boost torque with that low of a compression. It's given me something to think about. I'm pulling the head off tomorrow and inspecting the damage so that may determine what happens in the next few months.
I couldnt imagine the off-boost torque with that low of a compression.
What is this "off-boost" you speak of?
One of the things I plan on playing with is rotational idle... idle under boost... One of my friends has all those bells and whistles on his WRX and I rode in it and it basically doesn't feel like a turbo car, it's just BOOOOOOOOOOOOOOOOST
But he is running E85 which means he has to carefully map out his journeys and sometimes it's a Mad Max like search for "the precious juice"... and he can only run 17 pounds before he runs into issues anyway. i forget if that was because of knock or because that's just the limit of the turbo he has. Although the second can lead to the first.
How about you just run some normal compression ratio and then just switch programs depending on what type of fuel you are running? Just don't forget.
My archaic, 25 year old factory ecu has dual knock sensor knock control and with some very minor code tweaks it blinks the CEL on every detonation event. Yea it obviously has it's limits but I don't get why you VEMS, 034, and MS users don't have knock control or at least knock indication?
MS3 has knock detection. From speaking with Matt, you can tell it what frequencies to look at and in which angles of crank rotation to look at, and which knock sensors read what cylinders, to help distinguish between engine noise and knock. Just like the OEMs do. (This after conversing with him when I mentioned planning to run FAST XFI and he said "Why? Their knock detection is nowhere near as robust as ours."
Funny thing is the MC engine block I picked up does not have the MC2's knock sensor bosses milled or drilled, they are just casting knobs. The first MC1 block I picked up had them milled, drilled, and tapped. Strange...
The only real problem with relying on knock control is that once it happens, you have by definition had a knock event. No big deal under cruise/light accel but knock under hard boost is going to be hurting things. Could be worse, though. I come from the land of rotors and under boost you not only avoid knock like the plague, but you also avoid misfire... because misfire is just as damaging as knock, and misfiring can LEAD to knock.
I couldnt imagine the off-boost torque with that low of a compression.
I think you could get away with 10:1 on e85, but it would be e85 only, don't even think about running gas through it on any boost.
Hank
E85 / Racefuel was the plan.
I'll be running e85/e98 in the Dodge with 10.0:1 compression on a vortec supercharger setup, but this is completely irrelevant to the 2v Audi designs. I'll still be able to run pump but just with an ultra-conservative tune (on the Dodge).
1986 4000cs Turbo Quattro
2001 Dodge Dakota R/T Standard Cab
1990 V8 quattro
1995 urS6
-Hersh Performance and Racing Products-
Most orders are being refused until further notice. Please PM
Noisy Cricket wrote:under boost you not only avoid knock like the plague, but you also avoid misfire... because misfire is just as damaging as knock, and misfiring can LEAD to knock.
This right here is clearly something I was dealing with... a crazy misfire that only happened after hot runs and progressively got worse at idle... drive it for 5 minutes and the misfire vanished... Matt, Chris & Kevin were in the car at Carlisle when slight signs of it started popping up...
No VEMS is not sophisticated enough (with my current firmware anyhow) to detect, monitor, warn or adjust for such events.
I'll be running e85/e98 in the Dodge with 10.0:1 compression on a vortec supercharger setup, but this is completely irrelevant to the 2v Audi designs. I'll still be able to run pump but just with an ultra-conservative tune (on the Dodge).
A friend is running 10.5:1 on his 4v mod mustang. It's stroked to 5 liters, CNC ported heads, cams, and a D1SC to name a few of the mods. On a 97 degree day it made 796whp on a mustang dyno. With a good base engine that has a high VE, 10:1 and higher can be done with boost on E85.
Just look at some of the SFWD and outlaw civics. They're in the 12:1 range running 40+psi
I'll be running e85/e98 in the Dodge with 10.0:1 compression on a vortec supercharger setup, but this is completely irrelevant to the 2v Audi designs. I'll still be able to run pump but just with an ultra-conservative tune (on the Dodge).
A friend is running 10.5:1 on his 4v mod mustang. It's stroked to 5 liters, CNC ported heads, cams, and a D1SC to name a few of the mods. On a 97 degree day it made 796whp on a mustang dyno. With a good base engine that has a high VE, 10:1 and higher can be done with boost on E85.
Just look at some of the SFWD and outlaw civics. They're in the 12:1 range running 40+psi
The concern is the Audi 20v head and the limitations that it imposes, low knock limit, not the compression ratio. I put a lot of miles on my stock 7a with 15psi from the H1C and no known issues, granted I still need to get a real tune but that will be better/safer so moot.
Mcstiff wrote:
The concern is the Audi 20v head and the limitations that it imposes, low knock limit, not the compression ratio. I put a lot of miles on my stock 7a with 15psi from the H1C and no known issues, granted I still need to get a real tune but that will be better/safer so moot.
100% understood. The heads flow terribly, but boost can make up for that (to a point). The detonation threshold is pretty low on the 20v chamber. If you look at the Nissan L28ET engine out of a 280zx turbo, it has similar CFM numbers to the 20v in stock configuration, similar compression ratios, 2v/cyl, yet 400whp isn't completely unheard of on a stock log manifold that is almost as poorly designed as the MC mani.
Now on that note. I am going to experiment with opening up the chamber a bit to help increase knock resistance. This includes adding more CCs by reducing the "ledge" and perhaps transforming it into a more cylindrical design such as those found in the domestic V8 motors. It will be interesting to see how I go about it and what I come up with
1986 4000cs Turbo Quattro
2001 Dodge Dakota R/T Standard Cab
1990 V8 quattro
1995 urS6
-Hersh Performance and Racing Products-
Most orders are being refused until further notice. Please PM
You keep doing that you will end up with one hell of a bald spot!
"If you can't find one, make one"
Dallastown, PA
1991 Audi 80 quattro (20vt project)
1991 Audi Coupe Quattro (project: my first 20v)
2007 Mitsubishi Raider(Dakota in disguise)
2019 Chevy Cruze RS hatch (wife's little red sporty car)
One of my friends has all those bells and whistles on his WRX and I rode in it and it basically doesn't feel like a turbo car, it's just BOOOOOOOOOOOOOOOOST
