I was thinking of about getting an LT1 Ported Intake Manifold, and a 1000 cfm 58mm throttle body. I know these mods will hardly do anything until I do some head work but I want to get the easy stuff done first. However someone told me that having this much airflow would hurt my engine. I was wondering is this true or not? If it is I will hold off on these mods but I really want to get these out of the way now too. So that is why I posted here, do you think those two mods could hurt my engine? I don't really believe it but then again I don't know enough to disprove it either.

Thanks,

Chris

 

ttt

 

Hurt as in physically or as in power? It may make you loose a little down low but thats about it. Id go for it if you want to get that aspect of your project completed (at least i would FWIW).

 

There is no such thing as too much airflow... get the air into the cylinders and the PCM will add the required fuel.

But you have to understand that just because you buy a throttle body that someone has labeled "1000cfm" does not mean it will flow 1,000cfm on your motor. Because it is larger, there will be a tiny reduction in pressure loss through the bores at the 400cfm or so that your engine needs. That means there will be a tiny increase in the pressure available to fill the cylinders, and that means there is a tiny increase in the density of the air, and hence the "mass" (pounds of air) in the cylinder. If your engine only needs 400-500cfm, that's all that will flow through the TB and the intake manifold.

I believe that there may be some shifting issues with the 58mm TB, if you have an A4.

I would also question "porting" the LT1 intake. Everything I have seen or heard, including extensive discussions with the people why did my heads - and were involved with the development of the LT4 setup - is that the LT1 intake needs little if any work to support very healthy LT1 heads. Might want to save intake porting until you have some heads to port match to.

 

To add my two cents in here: I think the larger throttle body would make the throttle response feeling pretty ridiculous. All your throttle from closed to WOT would be before the blade gets 50% open I'd bet. The last 40-50% of throttle angle would be useless. Or maybe I'm off here...

Not to derail this thread too much.. but Fred:

Can you explain why the LT4 intake seems to need so much more work than the LT1? I never have understood this. I am just wondering about the technical aspect of it. I thought it was just a raised runner version of the LT1...

 

Also have to consider that it doesnt actually flow 1,000cfm. Those TBs cfm ratings are at 1.5" Hg, So convert it to 1" and its actually 816cfm

 

I only know what people have told me. Pete (Incaudo???) at CNC Cylinder Heads in Florida claimed to have been involved in the development of the LT4 engine for GM. He claimed that the LT1 intake was fine "as is", but the LT4 need extensive work to flow well with high flow LT4 heads. He said that there were "emissions compromises" that were included in the LT4 intake manifold. Maybe that was just a pitch to justify $300 worth of intake porting, but when I got the intake, there was a he!! of a lot of work done on it.

All this is "what I've heard"..... but.... everything Pete told me about the intake flow was true. His LT4 heads flowed very well on the intake, and when they were flowed with the CNC ported LT4 intake, flow INCREASED by 3%. The shop that did my flow work could not duplicate this with George Baxter's LPE CNC LT4 heads and intake.

Unfortunately, the CNC work on the exhaust ports was a disaster, and they refused to talk to me about it.

 

Yeah but guys from what I have read the only way a 58mm throttle body can fit on my car is if I get a ported intake. For some reaosn it seems that is the only way a 58 mm will fit. Are these sites telling the truth or is this :BS:?

 

You have to define "ported".... to me that's improving the flow of the runners. But if you mean bore the throttle bores to 58mm, yes, that's the only way you will see the full benefits of a 58mm TB. If you check Brent Franker's how-to website, he shows how to open the bores up to 58mm with the intake on the car. Not sure I'd want to try it, but he had no problems.
Fred

 

Well, it's not true. The gm engineers may have initially intended the LT4 intake to be an asset to the LT4 heads, but the end result, IMO, is a joke. Certainly NOT a raised runner version of the LT1, regardless of what web sites may state. Maybe those web sites are reciting some original/initial engineer notes. The way I see it, is what they (gm) did accomplish with the LT4 intake, is make it heavier than the LT1 counterpart.

Also, I don't agree what most people are doing to adapt the LT4 intake to the LT4 heads either, again, IMO.

 

That may be, but I wouldn't mind a little more detail here. What differentiates it from the LT1 and what makes it so poor?

 

After putting the LT4 intake gasket up to the head, the bean counter is snickering, and the engineer is shakin' his head. Even after raising the port (glorified gasket match) to accommodate the head port, (IMO) the intake still doesn't mate well with the raised port in the head, due to the compromise of the approach angle.

After inspecting, measuring, checking, and some layout effort, bottom line, it is just a glorified LT1 with powder coating and extra weight from extra cast material above the port. It would have been nice, if GM would have REALLY designed a specific LT4 intake. I also liked (sarcsm here) the way they rectified the LT1 head/intake plenum intake port mismatch. Hint; it's ironic the 'correction' came at the time the LT4 intake was made available. Oh, they knew what was going on there, just no money allocated to do the job right. (editorial... )

 

My understanding on the 58mm TB installs is that for manual cars, it isn't as big an issue. But for A4s, it can cause shifting issues.

You WILL have to open the bores on the front of the intake where the throttle body mounts to take advantage of the full flow, but that's nothing too difficult.

 

Hold on a sec. Has anyone ever dynoed a 58mm throttle body on a fairly stock engine? From back in tech school, when installing a 52mm on a stock engine, the car lost 10 hp. My instructors had us do that if make a point. From my understanding, if the port is too big for the engine to handle, the volocity of air entering will be too low. Which makes sense when looking at the new BMW 745i and 760i with the throttleplate -less induction. Air is controlled by the amount of lift of the valve. Now the throttle housing on that car is not huge. I never measured the vacuum while accelerating near full throttle, but my guess would be it is low vacuum, but not zero, correct?

 

Oh yeah. Another question. By porting your mean...........enlarging the runners? Or port matching the heads and the intake?