If an L98 is a TPI motor what is an LT1?

[Paul G]

I hear the L98 motors refered to as TPI motors all the time. Just curious what the LT motors are called?

 

[WhalePirot]

The Tuned Port Injection era started in 1985 for Corvette, replacing the TBI. The SBC was redesigned and became the LT-1 and LT-4, with some interchangeable parts. All are port injected (TPI) but the 'LT' is a way to narrow down to more specifics.

 

[*89x2*]

...on the C4's

multi-port or sequential-port injection, depending upon the year of the (Lt1/LT4) Corvette


Cross- fire was 1984 only

Tuned Port was from 1985-1991

Multi-port was 1992-1993

sequential port was 1994-1996

 

[Ken]

The letters/number combination indicates the engine option code as designated by GM.

Engine codes have included the L49, L82, L83, the powerful L88 (a 427 cid engine from the late sixties), the L98, and finally the LT1, and the LT4. The new generation of small blocks switched to codes beginning with the LS designation, such as the LS1 and LS6 (which again was once a code for a high performance big block from the sixties), and the new LS7, which is a 427 cid small block.

There are more designation codes but I cannot recall them all at the moment.

 

[DRTH VTR]

Cross- fire was 1984 only

1982 also?

 

[tnovot]

1982 also?

True, dual TBI included 1982 also but if you go back to the heading on 89x2's post, it pertained to C4's. The 1982 was a C3.

 

[*89x2*]

1982 also?

...please see my above post - we are talking C4's here

Of course the 82 was cease fire...

 

[vader86]

Technically, the TPI system is a multiport injection system, both use a batch-fire setup. Its called "tuned port" because of the intake design being "tuned" for high port velocity at lower rpms.

Just call it an LT1/4.

 

[Aurora40]

I beleive Multi-Port Injection or Sequential Port Injection could also have just been called Tuned Port Injection if GM chose to go with that terminology. They all have one injector per intake runner. I think Sequential Port Injection simply improved the timing/control of the individual injectors firing, and was mostly possible due to microprocessor improvements. Engine controls just keep getting more and more advanced.

 

[Ken]

Okay guys, here's a little light reading from Fuel Injection Specialties for you to peruse:

The following information on GM Port Injection and GM Tuned PortInjection Systems has been compiled from GM published material and as a result of discussions with our technicians who have installed these systems on a variety of vehicles. It is to the best of our knowledge accurate.

GM Port Injection​

 

[G Winter]

Teachers and their darned homework!:crazy

 

[PLRX]

Don't forget the MIGHTY LT5
​

 

[Aurora40]

Don't forget the MIGHTY LT5
​

I would guess the LT5 was not sequential port injection? I don't know, though. But I'm not sure if engine controls were that advanced to fire/control each injector individually. The backfire thing on aborted starting would make me think the injectors are batch-fired on the LT5, at least on the earlier LT5's. Anyone know for sure? :confused

 

[Ken]

1990-95 ZR1 Corvettes are sequentially injected.

 

[KOPBET]

I would guess the LT5 was not sequential port injection? I don't know, though. But I'm not sure if engine controls were that advanced to fire/control each injector individually. The backfire thing on aborted starting would make me think the injectors are batch-fired on the LT5, at least on the earlier LT5's. Anyone know for sure? :confused

All ZR-1 engines were Sequential Fuel Injection. SFI pulses each cylinder seperately.

 

[Aurora40]

sweet!

 

[Brianjt1987]

I hear the L98 motors refered to as TPI motors all the time. Just curious what the LT motors are called?

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