wannagofastZ28

I have a 95 Z28 w/ six speed and just recently replaced the intake with a ported stock LT1 intake, MSD 8.5 wires, ignition coil, plugs, and water pump. The car seems to be fine, no leaks and seems more top end power. My issue is that before i could be doing 60-65 down the freeway in 6th and just casually increase speed now if i don't downshift to 5th it will chug along. It does this in all the gears when before i wouldn't need to downshift but now i do. Any ideas? Do i need to get the ECM tuned?

Tex95Z

Is it throwing any codes? How's the fuel pressure? Egr valve can cause that issue. However it's normal for the car to chug in 6th gear when you lug the engine.

Injuneer

If those are the only mods, you shouldn't need a tune. How radical was the porting on the stock LT1 intake? Generally there is very little, if any, benefit, from touching the stock intake, unless there have been corresponding changes to the heads.

wannagofastZ28

The stock intake was ported to match set of gaskets and claims to flow just as good if not better than Edelbrock or LT4. I only put it on because of intake gasket leaking and it will accomodate up to 58 mm throttle body. The car was already throwing the SES light on every now and then before and it still does but doesn't seem to effect the performance, never really did. I have looked high and low for a scanner to read the OBDI comp with an OBDII connector, but without purshasing and finding an OBDI scanner I was at a dead end. Also it is a six speed, and it has always idled at 1000 rpm, is this normal? There is no issue of the intake getting more air or anything like that right cause the MAF should adjust accordinly. The sticker on car says to gap plugs at .050, I put in some NGK TR55 iridium plugs. Is this correct? Does the car ever need to be re-tuned when stuff like this are replaced? Do they ever need to be re-tuned? Plan is to get the 58mm TB, some headers, and some kind of tune put on it, maybe have the heads done? Car does run strong(of course) at times it does ping though and all I run in it is super.

Injuneer

To cover all your points:

The Edelbrock LT1 intake does not flow better than the stock LT1 intake. It has a smaller plenum volume and has been dyno proven to reduce HP at upper RPM. The LT4 intake, as cast, is identical internally to the LT1 intake. It won't even support the LT4 head flow, and requires significant port work to do so. The only difference between the LT4 intake and the LT1 intake is the red powdercoat, and a bit more "meat" at the top of each runner to allow them to be opened up (ported) to match the LT4 raised intake runners. But the actual ports are the same as the LT1.

We have a link to a free download of 94/95 scanning software posted in a "sticky" at the top of the "Computer Diagnostics and Programming' forum. Far more than just a "code reader".

Stock programming for the M6 (coolant fully warmed up) is 800 RPM. The stock tach typically reads 100-200 RPM higher than actual. An indicated 1,000 RPM isn't out of the question. You need to use the scanner to get actual idle RPM.

Porting (gasket matching) the intake might have hurt more than helped. In any case, the change in flow is probably minor, and yes, the MAF sensor reads the actual mass air flow.

NGK TR55 Iridium are a good choice for the LT1. The second "5" in the part number means they are pre-gapped to 0.050". You don't need a "tune" for replacing external parts that are effectively the same as the stock part with regard to performance. Even going to a colder plug or a non-precious metal plug does not require a tune.

Unless you re pushing upwards of 500HP at the flywheel, you don't need a 58mm TB. The shop that built my engine was able to show me that at 496 flywheel HP on a fully instrumented engine dyno, my 58mm TB was only 77% open, and opening it further did not increase air flow. Back calculating, I could have been using a 52mm TB fully open. They still laugh at my 58mm TB.

You can gain 10-15HP with a tune on a basically stock engine. This is done by leaning out the overly rich PE (power enrichment) mode target A/F ratio. If you have a mail order tune done now, you will see a noticeable gain, and the tuner will usually offer a reduced price for future changes. Might want to check into that.

Tanya's Z

I cleaned my MAF and my car is running perfect. What an easy fix...who woulda thunk???