8.1 dbc tune

[Scooby1971]

I'm looking for a file to compare against mine. I have a stand alone 8.1 dbc. (Runs but just needs tuning)
No tranny (installed in boat)
Manifold baffle removed
Raylar 201 cam and roller rockers
No 02 sensors (marine manifolds)
Any help?? Thanks

[1970ss8.1]

What ECU are you using. I have a good tune in mine with rays 201 cam, baffle removed, 90mm Tb and roller rockers. Mine is using a gm p59 ECU blue green. But mine is dbw. I?m working right now on a tune for my chevelle. 8.1 203 cam, roller rockers, ported heads, 102mm DBC TB, custom intake, headers, bored out with forged internals.

[Scooby1971]

Well Im brand new to to this but I had a green /blue 2003 ecu with the 2003 engine. I had a guy helping me with it at first but the 03 ecu bricked so I bought a red blue ecu from a wrecking yard and repinned it. I bought hp tuners myself and I'm trying to learn how to run it. I know a lot about engines but I'm old school so I decided to buy hp tuners myself and see if I could learn something about ecu controlled engines. Does this tell u anything or do I need to find a ecu number somewhere? Thanks

[1970ss8.1]

You should be fine. Just make sure it has the IAC drivers. I know everything about 8.1?s. When I get home I?ll upload my tune. I?ve spent a lot of time building one for the 201 cam, but mine is blue green. I prefer them because they have mor memory.

[5FDP]

You better get a wideband o2 sensor if you don't have one yet.

It will be impossible to calibrate this correctly if you can't watch the air fuel ratio.

[1970ss8.1]

He is definitely right. Especially sense you aren?t running 02 sensors. You will need a tailpipe sniffer because you can?t weld a bung into the marine headers or you will destroy them. There are a couple people out there that can weld both sides of the water jacket in the headers but it will be expensive.

[Scooby1971]

Yes. I welded a bung for a wide band in the tailpipe right behind the exhaust manifold. The iac is working. I just have the idle surge that everyone talks about after installing a larger cam. I'm sure it would be a simple fix for alot of you guys on here but like I said I'm new to the hp tuners and just trying to learn. After I get it to idle nice I'll put the drive shaft in it and take it to the water where I can do some short runs with the wide band. I'm going to leave the manifold dry for short periods just to get some wideband readings. I will have to do a bit of research but I would think that a boat should run a little richer than a vehicle but I'll dive into that after I get it running nice in the shop..

[1970ss8.1]

The 201 cam is pretty small with a negative overlap, it shouldn't idle surge much. Check your adaptive spark. What fuel injectors are you running? the truck 36# or the marine 42#? Larry said with the 201 cam to just dial in the VE and it should smooth out. I dug a lot deeper into the tune than that. In marine form they produce the most power at 13.1 afr. Are your pistons stock? Look at my timing table it needs a lot more timing down low with the 201. It will launch really hard from a dig if you up the lower map area of the spark table. My tune is for 92 octane so if you use some of it you will pop a piston if you run 87 with stock hyper junk pistons. I also changes injector timing according to the 201 cam. From 2800 to 5000 you will want your pe to get you to 12.8 afr, any lower will bog the engine down when you hit pe. 21* is about all you will get with stock pistons and the stock iron heads. In marine form if you up fuel pressure to 60 - 65 psi it will gain tons of power, but that is with a mefi4 controller. Just make sure you remove the torque management, it neuters these 8.1s practically in half in the truck controllers. Upload your tune so I can take a look at it.

Finished tune for now.hpt

[Scooby1971]

2002_8.1_fish_rite_file_1.hptsparkchange2.hpt
hopefully i uploaded file right! this is a stock 2003 8.1 with manifold baffle removed,cable throttle body,raylar 201 cam and roller lifters, marine manifolds with wide band port for tuning only.stock Iat sensor and knock sensors are still in other wise its as bare as i can get it.

[1970ss8.1]

Is this the tune you are running right now? If so it needs a lot of work, the spark is extremely low. What octane fuel are you running? Did you go to a 90 mm TB or a 75mm?

[Scooby1971]

Well....I wouldn't go so far as to say that I'm running that tune right now..Lol. that is what I have in it at the moment and yes it starts but that's it. I usually run mid grade 89 octane fuel and I have the stock 75mm throttle body. I was told that with out heads and a larger cam that a large throttle body was no benefit to me...thanks for sending a copy of your tune! I am going to really look over it this weekend and try to learn some of this.