KeithO

I autocrossed my stock 88 IROC with the L98 yesterday. Since it was a slow course, I held the car in first for all runs. At one point I had a quick glance at the tach and was around 5,000rpm. I have a couple of questions:

1) Does this car have a rev limiter or should I be more careful?

2) If it has a rev limiter, where will it kick in?

Thanks. This old third gen gave the new Mustang GT's a handful yesterday. What great cars these third gens are!

Kevin91Z

iTrader: (1)

The stock TPI rev limiter is at 10,000 RPMs or so... You shouldnt have a speed limiter with a 350.

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West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

KeithO

10,000 rpm?! Is that a typo? I have to believe that the motor will come apart long before 10,000...

Is this just a way of saying that there is nothing to cut off the rpms if they get too high?

fb305svs

nah there isnt any rev limiter- i know with my lg4 though, its ignition breaks up BAD at 5000... sucks... becareful with the tpi though- the rolller cam helps with spoinning up, don go past 6k with it, its a watse of time!

Steve

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86 Firebird, LG4, t-tops, 2.73 open rear, SLP 3 inch cat back exhaust, catco cat, 1 inch carb spacer, Fiberglass cowl induction hood, Formula wheels, vette servo.

Current Plans: Waiting on: rear end parts- upgrading to 373's, 28 spline axels, slp zexel torsion posi, and a disk brake setup. Also have lowering springs, front struts, and hopefully a new mild 350.


My Webpage- Battle of the birds, My own Thirdgen Page, still under construction, http://www.geocities.com/soares711/index.htm

88 Firebird Formula- deseased 2/9/99- 305 TPI, SLP 3 inch exhaust, SLP Intake runners, SLP cam, 3.45 BW disc brake posi, WS6, NOS, and all that good stuff, 13.8 on the motor, 12.89 on NOS and slicks! Hit by what else!?!? a FORD EXPLORER!!!!!!

Grim Reaper

Kevin is correct. There is a fuel cut-off @ approximately 10,000 rpm. For all intents and purposes, there is no rev limiter - it is just set very high - like the MPH is set to 255 mph...you'll never hit it.

vortech305

if your motor is stock and u run the motor more than 5,500-6,000 rpm you'll destroy your ingnition system, oh and your motor as well.

JP84Z430HP

Also, isn't the stock TPI pretty much done at around 4800 RPM's? Something else to think about!

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Working on:
'84 Z28 LG4 305 with 200,000 original miles!
Added dual elec fans.
145 MPH IROC Speedo
Building 430 HP 350 (ZZ430)
using primarily GMPP parts.
Short block sitting on a stand. (Man, those Fast-Burn heads sitting on it look good!)

Starting to look like the Kicker poster child!

ASE Certified Master Tech

KeithO

So, if I understand this, the rev limiter is really 10k and there is a speed limiter at 255 mph.

Are you guys pulling my leg?

I'm interested in the comment about the L98 being done at 4,800. What is the limitation here? Is it the ignition, fuel system, what?

Just to be more clear - I say that I was around 5,000 because I glanced down and saw the tach past 12-o-clock headed for 1-o-clock at the end of a straightaway... If really did go past 4,800 it still felt as smooth as silk, pulled OK and sounded wonderful (cat-backs installed)! Even my wife commented on it - then worried I was going to break it...

I am not sure if I want to do this to the motor again. Any opinions here? It's got just under 90,000 miles on it. Note that under stock rules I cannot do much of anything aftermarket to the motor.

Thanks all.

JoelOl75

I rev my stock bottom end to a hair over 6,000 rpm with never any problems. The top isn't stock, but the pistons and rods never blew out the side.

Fredzep

iTrader: (1)

I ran my Rebuilt L98 (ZZ-9, S/R Torquers) between 5500 & 7000 at the track. I am now replacing the high rev lifters, cap & rotor, and coil wire. The 7K was on a over rev.
Next mod, 6 AL with rev limiter!
Be careful!



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Fredzep
90 GTA 350 5Spd
TPIS, SLP, Borla, K&N Mods

fb305svs

dont go above 5000... tpi dies at 5000 because of the induction system... put some runners, an aftermarket base and a bigger trottle body, and an inductionsystem, now ya can rev, but all in all, your muchbetter off hittin the next gear at 5k

Steve

vortecfcar

they werent pulling your leg. There seiously are limiters at those points.

pretty goofy huh

KeithO

I guess 10,000 and 255 just blew my mind... I suppose I have to believe, though I'm laughing because it seems to pointless...

I need to be more careful I suppose.

Grim Reaper

Those "fuel cut off" limits can be changed within the eprom. On cars that did not come equiped with 245/50/16s, the mph fuel cut off was set around 120 mph IIRC.

The rev limiter being set around 10,000 is a bit silly. I set mine to around 5,800 and the "enable" around 5,500. I still never take my engine that far, but I thought that would be a good safety margin.

Both Kevin and I burn our own eproms, so this is how we know about this limitation.

KeithO

I suppose I'll be careful on the revs.

As far as the tire size is concerned, I do have the bigger rims on the IROC. I understand that in 1988, the 16" rims had be ordered (defaulted to 15") on the IROC. Shouldn't there be an RPO code for the wheels? The reason I ask is that I have been able to chase down all but 3 RPO codes for this car and none of the decoded ones described 16" wheels.

The reason that this is important is I plan to run on a road racing course in June (Nelsons Ledges in Ohio) and I'd hate to bump into a speed-triggered fuel shutoff on a straightaway. Based on the track layout, I have to believe I'll exceed 120mph...

Thanks to all.

Kevin91Z

iTrader: (1)

As I said, I've never heard of an L98 with a 120 MPH fuel shutoff. That was only in the 305's and probably V6's too.

leirch

Keith,
Find out what the broadcast code is on your prom, we can tell you if it has a limit as far as speed is concerned(which i don't think it does, as Kevin stated). The broadcast code is inside of the computer. If you want to check, just drop the computer, pull the memcal, take the blue cover off and on the prom(black 28pin chip) you should see a 4-alpha charater code, something like AUJP?
And if you don't feel like doing that, just go out on a favorite country road at 2-3am and see if it has a limiter


Brendan

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1987 IROC-Z L98,SuperRam,EB 6085's,LPE 219/219 Roller, Crane 1.6RR, EB TPI Base, 58mm TB, ADS 24#, AFPR, K&N, EB TES, Catco Cat, 3" Borla Cat-Back, Accel cap,rotor,distro/other crap, MSD 6AL, MSD Blaster 3, Aluminum DS, 94 Disk Rear, Adjustable Valve, Precision 3.73 Gears, Sub-Frame Connectors, Hotchkis Lower Control Arms, KYB Shocks/Struts, Suspension Techniques Lowering Springs, Polyurethan Bushings all over the place, Moog Upper/Lower Ball joints and Tie Rods ends/Idler Arm,

To see the ROC, Check out the webpage Here

Vader

To be more exact, the speed limter was set at 118 MPH or as close as the VSS divisor could get to that number with a given rear gear ratio. For as accurate as factory speedos are, it's close enough.



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Later,
Vader
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"What a Day..."
Adobe Acrobat Reader

84TransAm

And Vader lays down the law....

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--Steve S--
1984 Trans Am 305 LG4, 5 speed Daily Driver, Flowmaster 80 Series
Holley 600 cfm & vacuum advance Soon: Edlebrock Intake & TES

Enkil

And the reason FOR this is...

The same EPROM (basically) is used in 305's and 350's. The 305's came with the speed/rev limiter set around 120, and the rev limiter set to umm.. yeah. SO anyways, there's been speculations as to the reasons for this (safety, insurance, liability, etc.) with the 305's. However they didn't want to put speed/rev limiters into the 350's. However, they were stuck with the problem of having two empty values in the EPROM that had to be filled. It's not like they could set it to 0 (wouldn't THAT be fun), so instead they just put in the highest value possible.



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89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else