I just got done driving my dads LS1 and I hit the limiter when the tach was showing 5400-5500 and the limiter is 6250. This has me worried that the LT1 tachs might lag behind too since I'm doing a T56 conversion right now. I have a 97 so it has teh same gauge cluster as the LS1's if that makes a difference. So do LT1 tachs lag at all?

 

Well since I added my AutoGauge tach, I have noticed right off the bat that the factory tach was off like 1-200 rpms. Now I havent been able to do some hardcore WOT runs to see if the gap increases, due to the cold and wet pavement.

But maybe someone else can chime in here.

Mike

 

My 97 was 150~200 off. I only noticed it after a Autometer tach

 

The stock tachs read "high" a couple hundred, not low. Whether they "lag" i.e., show lower than the actual RPM, at any given time, is another issue, I believe. JMHO

 

When I took my car to the dealer... I had them connect the TEch-2 up to the car. I turned my digital guage on and suprisingly...atleast on my car... every thing was matched right up with the TEch 2 readings. But I noticed that my Digital tach... is much quicker than the Stock tach when hitting higher RPM's ...just my personal observation...

 

LS1 tachs lag really bad in 1st gear, LT1 tachs do not. LS1's use a different set up for their tachs and that is why they lag so bad.

 

Do the 97 LT1's with the same gauge cluster as the LS1's use that same setup as the LS1's?

 

i noticed it was off by like 200 rpm when i put my autometer in, and its plugged into the ignition box so i trust it a bit more than the stock.

 

I noticed this too. When my car was an A4/2.73 it always shifted at a tach indicated 6k rpm, which it's supposed to be 5700 as i've always seen on the boards. Never could tell with the M6. But now that it's a A4/3.23 setup with a factory 3.23 program via MadZ28, it still shows 6k shifts. So mine is at least 300rpm too high on top end. It shows 750rpm at idle like stock LT1s are supposed to be at, so it's accurate at low rpm. It also shows about 2400rpm at 75mph in OD, but from all the gear calculators it's supposed to show about 21-2200rpm with the 3.23s. I remember that it showed about 2150rpm at 80mph with the 2.73s, but the calculators show 2k even at 80. It gets farther off the higher rpm you turn.

So who knows, i guess an aftermarket tach is the only way to really know what rpm you're turning.

 

I dont think the stock tachs "lag" at all. If you rev the motor up out of gear you can see the tach responds instantly so it definitely doesnt appear to lag behind the true rpm of the motor. Of course at the track you arent reving nearly as fast as you could out of gear so I am guessing the stock tachs really cant lag.