Rev limit advice needed

[pocket-rocket]

Weights and springs are for non electronic distributors. Carbs are jets and needle valves, mostly IIRC. He has it easier for tuning when it comes to fine tuning fuel. Large changes to the carb means it comes apart and jets are changed out. When in fine tuning he takes a screwdriver with him to turn the screws (with the needles on the end) one way or the other for fueling adjustments.

On a side note, I've always heard the joke as being the nut loose behind the wheel, lol.

[Schmieder]

Carbed, I see. When I said narrowband, I only meant for the pcm to get a true signal. I would go nuts if I had a narrow band gauge. Like watching two fine ladies play tennis in skimpy skirts.

Tuning, yes its laptop and fuel injection. I didn't realize you are carbed. But isn't there weights and springs to tune your carb? Like make it run a little richer at WOT?

I'm not a carb guy......

Being leery will keep the pieces off of the pavement though

Haha, yeah.

The only thing a good mechanic can't fix is the Nut behind the Wheel.

[pocket-rocket]

Being leery will keep the pieces off of the pavement though

[GM Ontairo]

It's funny you guys mentioned corky bell's book. The first thing I did after I bought the blower was read that. I remember the section you are referring too. It has something to do with when the load builds and releases at the moment the crank is dropping from tdc. I don't think I could explain it and have it make any sense at all but I remember reading it and understanding the concept. So I can see the point you are making and I agree with you.

You also raise a good point about the wideband a/f system. I've got about $70 in this a/f set-up at the moment and it was just sort of an afterthought. The narrowband is just a lightshow at best. My favourite part is when the lights come on like a fan all the way from rich to lean, I'm going huh? I'm focusing on another project right now so the priority just isn't there. The current narrowband might not tell me exactly what base I'm on but at least it'll let me know what ballpark the game is being played in.

On the subject of tuning. I'm carbed with a distributor so tuning is limited. When I hear the word tuning I think laptop and fuel injected. Don't get me wrong there is definitely some things I can do, however I can't really cut fuel out at certain times or richen it at others like a nifty f/i set up can.

As I previously mentioned I like to take this truck out on the road course so it sees anywhere from 2750-5500 rpm for a couple hours at a time. I did turn it up to 5500 from 4500. I'm afraid to push it much more then that for extended periods of time. If I was drag racing I could understand going up more because it would only see peak rpm for a short instant before dropping again. Where as I can hold that peak rpm through a turn for as long as 5+ seconds. Maybe I'm just being a little to leery.

[Schmieder]

Hey, this kind of thing is what these sort of boards are for

If you read Corky Bell's book Maximum boost, you will read that, yes, load levels do go up, but not extreme amounts. I will have to go back and reread that section to find out just how much they go up and get back with you, unless someone else who has read it recently remembers.

I agree, Maximum Boost is a great read. It helped me build my turbo.

My car is proof you can run 8psi on stock springs. I had on rare occasions spiked to 12psi while tuning up the MBC/WG Spring and it wanted to go go GO! I would wind up to 6500 often, but no more. Just because I didn't want to, not sure if my build could do it or not w/o valve float.

The camshaft in my 3100, pretty sure others are the same, is actually really good for turbo. So you have the advantage there already.

I am now a firm believer of "It's all in the Tuning". There are people who push large amounts of boost on stock internals for years w/o a problem. All these people had 1 common advantage, the engine was tuned very well.

Detonation, running lean/rich, etc is where most problems arise from. As an example, I choose Hypereutectic Pistons over Forged. Hypers do not expand much and are great tolerating heat. The only down side is they are brittle when they encounter detonation or peak pressure occurs to soon for what ever reason. But a good tune and a spark knock detection tuned good will keep my hypers happy for a long time.

If your gonna boost, you need to have the ability to tune yourself. Many will say you don't need to but I wouldn't. ANd a good wideband AFR is a must too. But your Narrowband AFR should be replaced to ensure accurate stoich readings...which the WOT depends on concerning fuel trims.

[pocket-rocket]

I'm just trying to gain a better understanding of the physics involved here. So please don't take this as me questioning your statement.
From my understanding an engine under boost will see higher loads. So for a N/A to run 7k in comparison to a 5lbs running 7k there is a good bit of difference in the stresses happening to the components. If I'm mistaken someone please feel free to correct me.

Hey, this kind of thing is what these sort of boards are for

If you read Corky Bell's book Maximum boost, you will read that, yes, load levels do go up, but not extreme amounts. I will have to go back and reread that section to find out just how much they go up and get back with you, unless someone else who has read it recently remembers.

[Schmieder]

The springs are brand new and just inspected prior to installing the blower. The trans is a non wc T5 in it right now. So shift points is a non issue. Could you care to elaborate a bit more on your set-up? 8lbs, sounds like you are in the neighborhood I would like to be in.

My valvetrain is stock but rebuilt all around except for the camshaft. New heads w/ mild port myself (just simple floor smoothing, pocket clean up and exhaust polish) I did deshroud the valves though, my cylinder heads are truly unique now. They run great under the autotrans.

So the springs are new. I also replaced the timing chain just in case.

Here is the list of stuff I did so far.......it is a bit long, lol.

32lb injectors, new KB hypereutectic pistons, chromoly rings gapped myself for boost w/ the hypers, tri-metal rod bearings, ARP connecting rod bolts, crank scraper, walbro high flow fuel pump, MLS head gasket at oem thickness, modified UIM gasket (oem leaks easy), new solid motor/trans mounts, 180° T-Stat, Oil cooler pre-turbo oil feed, T04E Turbo at .50/.63 trims, external wastegate w/ 4-6 lb spring, simple boost controller, small intercooler, 3" BOV w/ modified spring, custom welded cross-over to turbo manifold, 2.5" mandrel bend exhaust, "fake" catalytic, dual flowmaster 40 mufflers, cherry bomb resonator, several flex joints, Heat wrapped exhaust from heads to DP, wideband afr gauge, oil press/temp gauges, boost/vac gauge, HP Tuner suite, swapped a 97 Lumina PCM (I had 96 GP, no HPT support), Getrag 282 w/ EP LSD, new hubs, axles, trunk mount battery....................

Not all of it is needed but some I would not boost to 8psi w/o. All stock (except for injectors, fuel pump) should handle 5psi safely.

[GM Ontairo]

N/A 3.4 DOHC. There's Fiero guy that had a 3.4 DOHC in his car with basically a shoebox for a plenum sitting on top of the LIM and spun his to over 8k on the dyno. I would say you don't have to worry about the rods.

I'm just trying to gain a better understanding of the physics involved here. So please don't take this as me questioning your statement.
From my understanding an engine under boost will see higher loads. So for a N/A to run 7k in comparison to a 5lbs running 7k there is a good bit of difference in the stresses happening to the components. If I'm mistaken someone please feel free to correct me.

If the springs are in good condition you should not have any problems at 6500. I had a limit of 6200 because my max shift occured at 5800 rpms. But it was built w/ cam advance for more grunt, so my power region was a tad lower.

I personally would set the limit 500 RPMS higher then the max shift rpm. And I would have the trans shift before the power starts to nose dive, letting it land back in the 'sweet' spot.

But I also beat the piss out of my transmission into near failure. I think I was subconsciously giving myself a reason to do a manual swap.

It was a stock 4t60e behind 8psi of boost.

The springs are brand new and just inspected prior to installing the blower. The trans is a non wc T5 in it right now. So shift points is a non issue. Could you care to elaborate a bit more on your set-up? 8lbs, sounds like you are in the neighborhood I would like to be in.

[Schmieder]

If the springs are in good condition you should not have any problems at 6500. I had a limit of 6200 because my max shift occured at 5800 rpms. But it was built w/ cam advance for more grunt, so my power region was a tad lower.

I personally would set the limit 500 RPMS higher then the max shift rpm. And I would have the trans shift before the power starts to nose dive, letting it land back in the 'sweet' spot.

But I also beat the piss out of my transmission into near failure. I think I was subconsciously giving myself a reason to do a manual swap.

It was a stock 4t60e behind 8psi of boost.

[Mars]

I'd run that to 7 if it still makes power there.

[pocket-rocket]

N/A 3.4 DOHC. There's Fiero guy that had a 3.4 DOHC in his car with basically a shoebox for a plenum sitting on top of the LIM and spun his to over 8k on the dyno. I would say you don't have to worry about the rods.

[GM Ontairo]

^ Sorry I'm not really familiar with your set up. Are you running a power adder or n/a?

[pocket-rocket]

I've spun my engine just over 7k countless times (rev limiter set at 7150 RPM). We have the same rods since yours are stock, and my bottom end is bone stock and not balanced.

[GM Ontairo]

The cam is pretty mild,

Valve springs are just stock replacements. The entire valve train was replaced with new.

If you had the 3.1 crank turned down on the mains do you know if the lead in oil grooves were cut back in? I ran both 2.8's and 3.1's hard before and that was the fix for spinning rod bearings. If they are there it should live just fine at 6500 like betterthanyou posted.

I spoke to the guy who did the machining to the crank today. To be honest 95% of what he said was just way above my head. So trying to repeat is going to make me look pretty foolish, something about enlarging the radia of the cheek and a bunch else haha. I would probably have to get him to draw me a picture to actually understand. He did however say oiling should not be a problem at all and that the crank is now stronger then it ever was stock.

Thanks for all the input guys it's much appreciated. This leads me to my last question, (that I can think of at the moment)

What are the rods rated to? Is it just 7000rpm? If so then running it to 6500 on a boosted application is going to be pushing it a lot is it not? So far no detonation problems as I'm running it slightly rich with not a lot of timing. I know getting into these rpms detonation can do some damage verrry quickly.

[Superdave]

You may run into valve float but that depends on your valve springs. Mechanically you should be fine up to 7K but i'd say 6500 is a safe limit.