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Thread: 7M-GTE, improve midrange: cams or ex housing swap, suggestions/ideas?

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    Junior Member Automotive Encyclopaedia HKS_TRD's Avatar
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    Default 7M-GTE, improve midrange: cams or ex housing swap, suggestions/ideas?

    OK the thread title probably isnt ideal but anyhow heres what I have been thinking lately maybe someone has any ideas or has been through a similar situation with a different motor.
    For those who arent familiar the main bits of my setup are a MOTEC M-800, GT35R with 1.06 exhaust housing, HKS 264 /8.1mm lift cams. It has all been extensively tuned but I feel the midrange is just not doing it for me, now I know I have a reasonably sized turbo and I plan to go from the standard 3.727 rear to a 3.909 or 4.11 in the near future but not sure if the power curve should be better. Boost comes on very early but it doesnt make any real power till past 4,000rpm (more like 4,500), limiter set at 7,000rpm.

    My thoughts are either put the stock or smaller (good luck finding any 248 or 256s tho) cams in, or a smaller exhaust housing or maybe both. I know I may drop peak power but so what, I could always put the T-04Z comp wheel in while the turbo is apart. I know the HKS cams made the midrange really weak when they were installed back in the day when I ran a high flow CT-26. However, I am wondering if with the GT35R even if I go back to stock cams will the power curve not change much because of the larger turbo. People have suggested that the cams and turbo if anything complement each other and just change the gearing

    If anyone can share any similar dealings they have had that will be much appreciated. I sort of miss the quick response of the old setup when you tickle the accelerator at lower rpm, but the fact this setup makes more power on less boost and has awesome top end out in the country does make up for it I guess
    Last edited by HKS_TRD; 28-12-2006 at 04:03 PM.

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    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Re: 7M-GTE, improve midrange: cams or ex housing swap, suggestions/ideas?

    could you start by adjusting cams to reduce overlap to see if it brings the midrange up? if it does, then cams might be first step.
    both will probably help, but it depends which is the limiting factor.

    can you borrow a stock cam?

    7000 seems a bit low for 264's on a boosted motor? are the cams tapering off by then or is torque still strong?
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    Junior Member Automotive Encyclopaedia HKS_TRD's Avatar
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    Default Re: 7M-GTE, improve midrange: cams or ex housing swap, suggestions/ideas?

    Hi there thanks for the reply, the cam timing has been tuned on the dyno, it used to be worse interestingly it responded more to adjusting the exhaust cam than the intake cam IIRC, this was done with the hi flow and then played with again after the MOTEC was put on. 7,000 rpm may not be alot but it is a long stroke 7M after all, the cams dont have alot of lift really (30 thou more than stock) power peaks about there IIRC. I'm going to talk to my tuner some more about it when he is back from Holidays

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    Junior Member 1st year Apprentice WeekendWarrior's Avatar
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    Default Re: 7M-GTE, improve midrange: cams or ex housing swap, suggestions/ideas?

    mate i would go to a slightly smaller turbo with the smaller rear hosing somethin like a 3037 or 2835 would give you brilliant tourque and midrange. your only going to seven grand which is not that excessiv. i have always used a rule if u can get 3500rpms or more of solid power than thats ok u should set ur self up to be getting full boost atleast 3500rpm before ur limiter hits and if u were to go a 28/35 or the 3037 i think you would be pleased.

    either that or just to a smaller rear housing will get u out of strife.
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    Teh Massif Dong Carport Converter BlackSupra's Avatar
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    Default Re: 7M-GTE, improve midrange: cams or ex housing swap, suggestions/ideas?

    Dan, maybe try a .86 rear housing on the 35R or look at disturbed1's GT3040 and how responsive that thing is!

    My motor also suffers from lack of midrange under 4000rpm so i know what you are taking about.

    Im going to look to remove and resize my intercooler piping for a shorter path and increased air velocity.

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    Junior Member Backyard Mechanic jezza323's Avatar
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    Default Re: 7M-GTE, improve midrange: cams or ex housing swap, suggestions/ideas?

    another way to bring the torque curve back down the rev range (at least in n/a, not sure on how it applies to boosted engines) is to lengthen the intake runners.

    if you have room, you could test it out by making a 20mm (or more) spacer plate to go between the intake manifold and the head, and whack that on, see how you go. but as i said, not sure how it would work with a boosted motor
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    Default Re: 7M-GTE, improve midrange: cams or ex housing swap, suggestions/ideas?

    Quote Originally Posted by BlackSupra
    Dan, maybe try a .86 rear housing on the 35R or look at disturbed1's GT3040 and how responsive that thing is!

    My motor also suffers from lack of midrange under 4000rpm so i know what you are taking about.

    Im going to look to remove and resize my intercooler piping for a shorter path and increased air velocity.

    What turbo and what size camshaft have you got in your motor? I am keen to try the smaller exhaust housing but I reckon its the cams that are doing it, even the hi flow felt doughy when the cams went in, maybe I need to get something with less duration and more lift but then the head has to be machined and I'll need under shim buckets. What we need to know is if anyone runs a 35R on a 3 litre motor and gets good midrange. I could always put an auto in it with a 4,000 rpm stall converter!

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    Default Re: 7M-GTE, improve midrange: cams or ex housing swap, suggestions/ideas?

    Hey mate

    If I was you, particularly given the big overdrive on the R154, I'd have no hesitation in going straight to 4.11's... that will really liven up a heavy car and it's a cheap & easy swap. The beauty is that if you don't like it, pretty easy to swap straight back again.

    What we need to know is if anyone runs a 35R on a 3 litre motor and gets good midrange.
    You shouldn't have any problems with lacking midrange on a 7M, unless maybe you're imagining a deficit due to the bigger top end rush. The 35R is a great turbo and should be perfect for your application; I've spent a fair bit of time in a friend's RX3 with a 13B and an 1100hp-spec GT45R and midrange/part throttle driving is fine. Admittedly a much lighter car but the motors have equivalent exhaust flow characteristics and that turbo is a shitload bigger than yours.

    The other thing to do might be to speak with a turbo expert, wheel trims (in the turbo, not hubcaps! ) can have a huge impact on power characteristics so you might want to look there as an option.
    Last edited by Shifty; 29-12-2006 at 10:36 AM.
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    Junior Member Automotive Encyclopaedia HKS_TRD's Avatar
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    Default Re: 7M-GTE, improve midrange: cams or ex housing swap, suggestions/ideas?

    Quote Originally Posted by Shifty
    Hey mate

    If I was you, particularly given the big overdrive on the R154, I'd have no hesitation in going straight to 4.11's... that will really liven up a heavy car and it's a cheap & easy swap. The beauty is that if you don't like it, pretty easy to swap straight back again.



    You shouldn't have any problems with lacking midrange on a 7M, unless maybe you're imagining a deficit due to the bigger top end rush. The 35R is a great turbo and should be perfect for your application; I've spent a fair bit of time in a friend's RX3 with a 13B and an 1100hp-spec GT45R and midrange/part throttle driving is fine. Admittedly a much lighter car but the motors have equivalent exhaust flow characteristics and that turbo is a shitload bigger than yours.

    The other thing to do might be to speak with a turbo expert, wheel trims (in the turbo, not hubcaps! ) can have a huge impact on power characteristics so you might want to look there as an option.
    Hi mate, yeah I agree I'm going to try gearing first, I sold the OS gear set I had because the ratios were wrong for the street. I am tossing up wether to go a 3.9 or 4.1 rear I still want to be able to drive it in the country and not have it rev off its head so that rules out 4.3 which is the only ratio I have at hand right now. I need to install my Cusco LSD so its no real inconvenience at all, though I want to get the speedo drive gears sorted out too

    I am seriously thinking its the camshafts more than anything now. I'm curious if I go back ot the stock ones but keep the vernier gears how well it can be tuned and how much power I would really lose, I know one guy in the US had the same cams and took them out because he didnt like the power curve.....

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    Teh Massif Dong Carport Converter BlackSupra's Avatar
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    Default Re: 7M-GTE, improve midrange: cams or ex housing swap, suggestions/ideas?

    HKS 264 Degree Intake Cam (8.1mm lift)
    Toda 256 Degree Exhaust Cam (7.9mm lift) (very close to stock)

    Trust TD07 makes for a laggy spool up, im positive your car would have more mid range than my setup would.

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    Former User Conversion King Joshstix's Avatar
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    Default Re: 7M-GTE, improve midrange: cams or ex housing swap, suggestions/ideas?

    My puny little 2.0l 3S with a GT3582 with .82 A/R turbine housing is making full boost and hauling arse by 4500rpm in fourth gear. I know it's not an apples to apples comparison but if anything mine should be worse than you're seeing. I'm also running 266 degree cams with 10mm lift and oversize valves.

    What kind of revs do you see full boost at, in fourth?
    How heavy is the car you've got this engine in?
    Do you have any before and after comparisons dyno graphs for the cam install?
    There are a lot of people that like to run smaller cams on the exhaust of these engines, possibly you could swap only the standard exhaust cam back in.

    Actually do you have a dyno graph at all so that we can see what kind of power it's making through the mid range? Also what boost are you running?

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    Junior Member Automotive Encyclopaedia HKS_TRD's Avatar
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    Default Re: 7M-GTE, improve midrange: cams or ex housing swap, suggestions/ideas?

    Heres the dyno sheet. I'll havet to go for a drive on the freeway and figure out the exact rpm in fourth that it makes full boost. I'll say this tho it doesnt make full boost in first.

    Blacksupra thats interesting you have a smaller exhaust cam, I may have my wires crossed but I think 2JZ guys if they stagger cam sizes the exhaust camshaft is larger?

    You know I'll say this about these ballbearing turbos and how fantastic they are supposed to be, my observation is yes they do spool earlier but they dont make any meaningful power unitll the same sort of rpm as older style turbos, so you just get a smoother transition rather than a light switch power curve, dare I say they are over rated?

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    Junior Member Domestic Engineer myne's Avatar
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    Default Re: 7M-GTE, improve midrange: cams or ex housing swap, suggestions/ideas?

    Smooth power delivery leads to better control.
    If you dont like having a predictable engine, then I guess it is a bit overrated for you.

    I assure you though, while it may not be making full boost, it's still clearly having an impact on the power or it couldnt possibly be smoother.

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    Junior Member Automotive Encyclopaedia HKS_TRD's Avatar
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    Default Re: 7M-GTE, improve midrange: cams or ex housing swap, suggestions/ideas?

    Dont get me wrong I agree they are better than old style turbos, and yeah the smooth power delivery means it doesnt spin the tyres as much as other on/off power delivery turbos, but some people go overboard with how much better they are. Anyhow will be fun to fine tune my setup, with all the stuff I have done now is the pointy end of the wedge. One thing I know is that with standard rods revving a 7M-GTE past 7,500 rpm is asking for trouble, not sure if my TRD sump and oil pump and HKS inline oil cooler kit with remote filter would affect this at all tho.
    Slightly off topic but my head has net been ported AFAIK now what sort of effect would porting have on the power curve, and in relation to aftermarket camshafts?

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    Junior Member Domestic Engineer myne's Avatar
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    Default Re: 7M-GTE, improve midrange: cams or ex housing swap, suggestions/ideas?

    They're better because of that small change.
    On off power is quite dangerous and can catch even the most experienced people off gaurd occasionally.
    Also, since the power ramps up smothly vs leaping up, examine the torque curve difference. That area between the 2 lines, is the extra power you're getting with the ball bearing turbo. Are you seriously saying that you prefer a smaller peaky band than a wider smoother band? Even with the same peak power, the wider band will be faster.

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