'90 454 TBI build.... Looking for pre-advice

[dyeager535]

Open loop simply means the system isn't using the O2 sensor to correct fueling...which is why tuning a modified motor is a necessity. BBC setups (at least the early TBI ones) were open loop always in idle, and in common with other GM EFI setups at least at this time, went open loop under certain load conditions, very importantly WOT.

You can pretty much make the injection work with ANY motor. But the worse the vacuum signal, the more effort it takes.

I haven't paid someone else to do my tuning, I bought the stuff and work on tuning it myself. (with help every once in awhile )

If you can fit long tubes, run them. I don't know as I've seen a shorty header comparison to manifolds, but that is what's important, how they perform compared to manifolds. Long tubes are better than manifolds everywhere, and to my understanding (anyone have a link to a short tube comparison?) the short tubes help, but only in the upper RPM ranges. IMO on a truck motor not used at high RPM, you might as well stick with manifolds if you are thinking of short tube headers. The tradeoff in potential hassle just isn't worth it.

I'm not a fan of duals anymore. Depending on what you are trying to do, they clutter under the truck and have twice as many parts to fail. With the advent of 3" tube, the necessity of duals is pretty well gone for anything other than max HP efforts.

No ties to the cat that would require you running one. I think pretty much everyone, including GM, runs the O2 sensor in one bank. Makes it really easy to diagnose a problem if it's on that side, not so much if its on the other.

 

[Jester1]

I am just trying to imagine where I could cross over if long tubes are used. I plan on putting long tubes on the sub as it already has dual exaust. Right now it crosses underneath at the bell housing. I was only thinking shortys due to the location of the front driveshaft and the crossmembers that may be in the way.

Once again this thread is, for me, a discovery into something new for me and being able to put smart money into this build. only using products that will potentially yeild bang for buck.

What does it take to get into the stuff to tune for yourself?

 

[black dawg]

Are headers a big deal powerwise on a tbi big block?

 

[dyeager535]

I was looking at mine, it's either going to be under the bellhousing or under the driveshaft just rearward of the t-case, at least that's what I think now. I *think* even with long tubes it will still fit near the bellhousing, if they fit well.

Here is a picture. It will be a tight bend http://coloradok5.com/forums/showpost.php?p=2211545&postcount=61 Then again, that's a smallblock. Big block shouldn't be much different, but that's up to the header manufacturer.

Depends on how you want to get into tuning. There are a couple of different ways, I'm only familiar with one. I have this http://www.moates.net/apu1-autoprom-package-usb-version.html Depending on ECM, this is probably what you'd also need http://www.moates.net/g2-memory-adapter-0-60-leg-spacing.html The APU1 is fairly pricey, but you can make infinite adjustments. I did the whole separate PROM burning thing for awhile, but it got old, and just being able to run the whole thing off/through the laptop, and making changes "live" was worth it to me.

Theory behind headers should apply equally regardless of EFI, carb, whatever. Header gains are from scavenging in the case of the SBC and BBC (others like Olds have design flaws that flow alone will make a difference), and if the exhaust manifold design is similar, gains should be similar. Brand new OEM is getting closer to headers, but they are dealing with cost/warranty concerns that we aren't.

Very brief synopsis (not to be condescending), scavenging helps fill the cylinder prior to the intake stroke...meaning less work to get more air/fuel in.

Just read a car craft article that tested collector design, and most dyno charts you find will start at 2000RPM if you are lucky....as RPM's increased, 3" collector extensions made very large gains. But if the beginning of the test means anything, at low RPM's it looked like the 3" was giving up power to 2.5" collector extensions under the RPM's the test was measuring, which is where we typically need it. Test engine was a 383, so still closer to a small block than a big block.

You can get into the calculations of how much volume each cylinder ingests (454/8=57CI) to start figuring out pipe design needed for a given displacement, but that's still a rough guess. The header manufacturers have the primary pipe diameter figured out already, so the only place to play around is at the collector and after for most of us, and I tend to think going a bit on the small side is going to be better than large, as long as the engine is intended to be used mainly to get a heavy vehicle moving, and not spending large amounts of time at high RPM. The further back you get, the smaller the pipe can (and IMO should) be.