Ok so I building a 420a for the eclipse keep in mined this is going to be my weekend car not my dd. I am trying to decide if I should go 10:5.1 or 12:1 I will still be running pump gas. I can't run e85 cause it is not being sold around here I wish I had that option but once again I don't. the other parts I am going to be running are below this will be my set up.

crower3 cams
indy valves
afx ecu
and full msd ignition


Also the car is going to be staying non turbo so I don't want to here how I'm wasting my time not going turbo.

I'd go 10.5 with crower 2 wit springs. Msd not needed. The ecu yor using leads me to believe its an automatic, I'd do a manual swap(higher revs so you can get the most out of cams). An use a manual ecu. That way it will be fun. Pretty simple build.

12.0:1 can be done with a good tune, but I would like to stay with the 10.5:1 ratio on pump gas. A lot will depend on the cam and timing as well, but generally speaking that 12:1 compression will be a bit too much IMHO for pump gas. I would rather go with less compression and more timing than more compression and less timing.

Yea thats kinda what I was thinking to but I thought I would ask others advice.
thanks

kongo said:

I'd go 10.5 with crower 2 wit springs. Msd not needed. The ecu yor using leads me to believe its an automatic, I'd do a manual swap(higher revs so you can get the most out of cams). An use a manual ecu. That way it will be fun. Pretty simple build.

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its 5 speed

kongo said:

The ecu yor using leads me to believe its an automatic.

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Why?

As for 12 to 1 (I presume you don't want to build a 21 to 1 diesel ), that may or may not be a sticky wicket. I still believe that 12 to 1 can be done on pump, but until I actually do it, I won't say for sure. Keep in mind that if you do try to go 12 to 1 and it doesn't work out, you will be forced to either change out the engine or go MS (where you can adjust out any problems).

But I'm trying real hard right now to test out my theory on my daily.

MB

kongo said:

I'd go 10.5 with crower 2 wit springs. Msd not needed. The ecu yor using leads me to believe its an automatic, I'd do a manual swap(higher revs so you can get the most out of cams). An use a manual ecu. That way it will be fun. Pretty simple build.

Click to expand...

afx ecu's can only be used with 5speeds so you know.

i have 10.5 crower 2's and alot of other stuff. its my dd too i run on 91 pump gas and its fine after i worked out a few things. i still need to do a minor tune but its got pleanty of power. if you go look up bulletdsm he is a dsm wiseman on this website that has taken the 420a really far. he runs 12.1 and crower 3's but im not sure what kind of fuel he runs im thinking its race fuel tho or a mix of 91 and 110. if you had it tuned super good to your set up i think you can get away with 91, 93 ocatane if you have it available. if you do 12.1 you would need an ignition mod and you dont need msd. bulletdsm runs obx ignition and i havn't seen a faster n/a 420a out there. i have je pistions and when i talked to one of the techs he said he runs 11.25 on pump gas. just ask around you will find your answer.

I'm with Mark, I feel that with as big as the Crower 3 cams are that the 12:1 can be done without much issue, because most of the compression is pushed out because of the cam overlap. Maybe I'm hopeful but I think its very doable after what I've seen happen on 10.5:1 engines.

Dependent on how you tune the car, 12:1 will work fine. Running the bigger Cams will help to keep cylinder pressures down.

I think I'm going to go the 12:1 route I think I can get it to work I guess we will see.

good luck man you have to keep everyone posted on the outcome of your build im sure alot of people are curious to know.