O.K., I do know a little, the Z is obviously a TPI LB9 car and the RS is a TBI L03. But what is different about the internals of those motors, both 305's (compression, cam, etc.?). For 92' there is a 60 horsepower difference on paper beteeen a Z & RS T-5, where is it coming from, can't just be the different injection system and exhaust setup, right???

Thanks in advance for shedding some light...Alex

[This message has been edited by RED92 (edited August 16, 2001).]

 

The RS with the 305 has many bottlenecks: weak cam, heads, and exhaust manifold. The single air snorkel insufficient for an 8-cylinder engine but well enough for a 4-banger. Equipped with non-posi at 3.08 ratio for manual or 2.73 automatic. Steering box and suspension feels like soft. Horsepower is rated at 170 w/255 torque. For a little more horsepower, I would throw in headers, 1/2" TBI spacers and injector spacers from Turbocity.com, March underdrive pulleys set (2 piece set crank and alternator), K&N air filter, AFPR, Hypertech or Jet stage 2 w/160 stat or custom version chip from Fast Chip or Performance Resource plus all the free mods that can be easily obtained from this site. Any gearhead would incorporate a posi unit 3.42 and a better camshaft such as LT1. After all the mods people usually replace the engine with a 350.

The Iroc or Z28 on the other hand has a lesser bottlenecks; better heads, camshaft, bigger exhaust manifold, can be had with a TPI system although from 88-90 TBI came with stock on the IROC and Trans Am/Formula, superb handling, quicker/shorter steering gear box, bigger sway bars, wonderbar (IROC only). More horsepower
would mean swapping the Throttle body from the stock 48 to a 52mm, better runners, Chip, Airfoil, K&N, underdrive pulleys, Headers, and of course here we go again all the free mods again.

Im not bashing the TBI, I have an '89 Camaro RS TBI and '89 GTA L98 best of both third generation world. I took the RS from Chicago to Los Angeles via Route 66 and back without any problems. TBI is highly reliable but majority of people here will probably be in favor of a Z28/Iroc-Z......no doubt. It boils down to the person's preference.

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89 Camaro RS TBI and 89 GTA L98

 

CC-

Thanks so much for your lengthy and detailed response. It answers a lot of questions that I had. I have a very nice 305TBI RS and recently drove a piece of you know what 305TPI Z28 and needed to know why that Z still felt so much faster. By the way, what do the spacers on the TB and injectors do for you?

Thanks...Alex

 

Gotta love the Z28 suspensions. At any rate to answer your question about TBI spacers, here is exerpt from Camaro Performance by David Shelby. The TBI spacer which functions much the same way as a carb spacer does by elevating the TBI unit. This increases airflow potencial and improves fuel atomization. Dyno testing has shown that spacers alone will produce as a 12 horsepower increase.
I have the 1/2 inch spacers on my RS and it's a difference you can really feel. From one TBI to another it's worth it. Check out turbocity.com for more info.

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'89 Camaro RS TBI and '89 GTA L98

 

Yes it is the different intake and exhaust setup, as well as the TBI having a smaller camshaft.

TBI was the base engine for 88-89. In 1990-92, TPI was the base engine.

Just to give you an idea of the difference, my dad put a stock TPI intake on his stock TBI engine (same cam and heads), and gained 17 HP and 70 TQ to the rear wheels.


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1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-

 

WOW on that TQ number!