I am just finishing up getting the engine running and am now getting the car road worthy.

First question is do I even need to buy an IAT sensor for the intake elbow or can I just plug the hole?

Second do I need to have an 02 sensor in both headers? The headers I have now only have a bung in the one side, is that sufficient or will the car not run right.

Thanks

 

IAT is a critical sensor. Without it the car will run in limp mode. Put it somewhere in the intake tract. It doesnt have to be in the hole they provide though

92-93 LT1s and TPI ECM controlled LT1s only need one O2 sensor. 94+ use sequential injection PCMs and use one O2 per exhaust bank to better monitor combustion. One O2 simply wont cut it. With a proper tune, the rear O2s can be deleted. Their sole purpose is to monitor cat function

 

My memory is going blank, where is the IAT on an LT1? Can you put it on here...



Similar question to the OP...

I've got a '97 LT1 sitting in the garage to go in place of a '92 305 TPI motor. If I can find a 88-89 intake as pictured above, the LT1 IAT should fit there, correct? Would I need just the 'Y' portion and the rubber boot, or would I have to fab the rubber boot regardless?

 

You don't want to run the TPI intake on an LT1, it will choke the motor down bad trying to suck air through a small opening, best thing is use an LT1 bellows and put a filter on the end of it.

To the OP, you need to run both O2s on the motor

 

I think I do

I've already boxed in the radiator, and cut up the bottom of the intake box , thus pressurizing the intake (albiet slightly). I've seen a few threads on here about modifying and opening up the Y. I want to at least give this a try if it will work.

*note* This is for a roadrace car. Class rules state 260hp/310tq limit, so I'm not exactly looking for maximum power.

 

Then it won't be legal for road racing.

the 93-95 f-body LT1 was 275/325 '96-97 was 285/335 96-97 WS6/SS were 305/335. The '92 Y-body version was 300/330 '96 Y-body was 300/340, 94-96 Caprice/Fleetwood/Roadmaster were 260/330

These were all factory ratings.

 

rated is one thing, what it puts down on a dyno is another.

depending on the age/miles on the motor, most seem to put out 260/300.

256/298, 253/306, 252/290, 262/308 are the numbers posted by some of the LT1 4th gens in this region.

Rules state you can either add a restrictor plate to bring the power down or add weight (determined by a table).

I'm in CMC (230/300 limit) right now, looking to move up to CMC2 (260/310 limit), so I'm going the LT1 route (rules allow certain engine combinations)

My tired 305 TPI puts down 217/276 while a some of the guys with fresh motors put down 229/299.

Next thing that will blow your mind is I have to use stock exhaust manifolds.
One more, I have the option to use a T56, running a WC T5 right now. Current plan is to freshen up the T5 and continue to use that for the weight advantage. I've read enough Oh noes it will explode! and decided to chance it with the whopping extra 30hp/10ft*lbs over what it is rated for.

soooo... with that intake work? That way I won't have to mess with the current one. Just need to know if I will need the rubber part too or not.

 

It will really starve the engine and it will probably run out of steam before hit hits where the rev limiter is (I have mine set at 6200 rpm and it will pull past it). Think about how your TPI runs out of gas at around 4500 or so, it will be like that.

 

I had mine hooked up to that intake just as you have shown in the picture, I changed the intake because of what everyone is saying, Im not really sure I noticed a difference. And with a computer controlled car the ECU will compensate for less air/more air. Its not like the old carb'ed days...

 

The computer can't compensate for air the engine isn't getting.

 

Im just saying, I don't think using the TPI intake system will reduce the amount of oxygen getting in so much that it will throw off fuel trim too the point where mixture is uncontrollable. The ECU will determine how much fuel to add from MAF readings, and should also use the O2 sensor voltage too determine how the mixture is doing. In this case, where he is not worried about making maximum power, it will be fine.

 

It does reduce the amount of oxygen getting in, because it reduces the amount of airflow that is coming into the engine. Plus, it also heats the air up because you are compressing the air into a small space.

 

Yes, which is perfect for what he is doing. He has restrictions for power, putting the smaller intake on isn't going too be bad in anyway, AF ratio will still be right because it is a computer controlled engine. And like I said before I have used that intake and a custom intake with a K&N cone filter and didn't notice a difference. It will actually be under a small vacuum, refered too as "Ported Vacuum" ... no compressing there..

 

wow i didnt know that the tpi air inlet intake choked down that much. there are people on here with theirs modded that are running in the 400 hp range with no complaints at all. heck with a modded one we fed a 406 small block thru one that put down 437 to the wheels.

 

*shrug*



101k mile LT1 (a/c delete, no air pump, new valve springs) with stock (early) TPI upper intake with no modifications. Early TPI bellows from MAF to throttle body, rubber bit from Home Depot from MAF to intake. K&N filters. Entire bottom portion under the filters has been removed (the rain gaurds). After these three pulls, I replaced the lower intake with one that still had the rain gaurds, made two more pulls and it didn't make a lick of difference.

*edit* This is with a WCT5

 

Very strange graph for a LT1. They like the upper RPMs and that one falls like a rock well before 6K

Do another pull with the TPI intake disconnected just in front of the MAF and see how it changes

 

I think it's more the scale of the graph that makes it look like it falls like a rock.

Here's a buddy's LT1 dyno sheet. It's a 4th gen firebird with the stock intake.


It looks like it does better than mine, but if you look at the actual values, I don't see mine as being abnormal. In fact, at higher RPM, mine is a touch higher.

At 4000rpm both are about 310ft*lbs.
At 4500rpm both are about 300ft*lbs.
At 5000rpm both are about 275ft*lbs.
At 5500rpm both are about 250ft*lbs.

Again, I don't disagree that a more open intake will net a gain, but what I do disagree with is the OMG you're starving the LT1 of air! that has been posted here and there.

I did take it back to the dyno. Unfortunately, it was after installing a dual 39mm restrictor plate behind the throttle body. Brought my numbers down to 253/302 to comply with class rules.